Near-infrared (NIR)-wavelength observations of Uranus have been unable
to locate any infrared aurorae, despite many attempts to do so since the
1990s. While at Jupiter and Saturn, NIR investigations have redefned our
understanding of magnetosphere–ionosphere–thermosphere coupling, the
lack of NIR auroral detection at Uranus means that we have lacked a window
through which to study these processes at Uranus. Here we present NIR
Uranian observations with the Keck II telescope taken on the 5 September
2006 and detect enhanced H3
+
emissions. Analysing temperatures and
column densities, we identify an 88% increase in localized H3
+
column
density, with no signifcant temperature increases, consistent with auroral
activity generating increased ionization. By comparing these structures
against the Q3
mp magnetic-feld model and the Voyager 2 ultraviolet
observations, we suggest that these regions make up sections of the
northern aurora.
Bright radio emission_from_an_ultraluminous_stellar_mass_microquasar_in_m31Sérgio Sacani
1) A new ultraluminous X-ray source (ULX) was detected in the galaxy M31 with a peak X-ray luminosity exceeding 10^39 erg s^-1.
2) Radio observations found highly variable radio emission on timescales of minutes to days, indicating an extremely compact emission region.
3) The X-ray and radio properties of this source are consistent with stellar-mass black hole accretion near or above the Eddington limit, powered by a relativistic jet as seen in Galactic microquasars.
An elevation of 0.1 light-seconds for the optical jet base in an accreting Ga...Sérgio Sacani
Relativistic plasma jets are observed in many systems that
host accreting black holes. According to theory, coiled magnetic
fields close to the black hole accelerate and collimate the
plasma, leading to a jet being launched1–3. Isolating emission
from this acceleration and collimation zone is key to measuring
its size and understanding jet formation physics. But this
is challenging because emission from the jet base cannot
easily be disentangled from other accreting components. Here,
we show that rapid optical flux variations from an accreting
Galactic black-hole binary are delayed with respect to X-rays
radiated from close to the black hole by about 0.1 seconds, and
that this delayed signal appears together with a brightening
radio jet. The origin of these subsecond optical variations
has hitherto been controversial4–8. Not only does our work
strongly support a jet origin for the optical variations but it
also sets a characteristic elevation of ≲ 103 Schwarzschild
radii for the main inner optical emission zone above the black
hole9, constraining both internal shock10 and magnetohydrodynamic11
models. Similarities with blazars12,13 suggest that jet
structure and launching physics could potentially be unified
under mass-invariant models. Two of the best-studied jetted
black-hole binaries show very similar optical lags8,14,15, so this
size scale may be a defining feature of such systems.
Propagation of highly_efficient_star_formation_in_ngc7000Sérgio Sacani
This document summarizes a study of star formation in molecular clouds near the H II region NGC 7000. The authors surveyed NH3 and H2O maser emission toward the molecular cloud L935 located near NGC 7000. They identified five dense molecular clumps based on NH3 emission, which have similar gas temperatures but different levels of star formation activity. One clump located near the boundary of the H II region has a high star formation efficiency of 36-62%, suggesting triggered star formation due to its interaction with the expanding H II region.
This document summarizes a study examining the hypergiant star ρ Cassiopeiae. The researchers developed a model to explain ρ Cassiopeiae's variable mass loss rate, high microturbulent velocity, and Hα emission line profile using a stochastic field of shock waves in the star's atmosphere. Their model successfully reproduced the observed mass loss rate, microturbulent velocity, and aspects of the Hα profile using only one parameter - the maximum Mach number of shock waves in the atmosphere. The model indicates that thin, hot regions behind shock waves are responsible for the observed microturbulence and contribute to Hα emission.
The shadow _of_the_flying_saucer_a_very_low_temperature_for_large_dust_grainsSérgio Sacani
Os astrónomos usaram o ALMA e os telescópios do IRAM para fazer a primeira medição direta da temperatura dos grãos de poeira grandes situados nas regiões periféricas de um disco de formação planetária que se encontra em torno de uma estrela jovem. Ao observar de forma inovadora um objeto cujo nome informal é Disco Voador, os astrónomos descobriram que os grãos de poeira são muito mais frios do que o esperado: -266º Celsius. Este resultado surpreendente sugere que os modelos teóricos destes discos precisam de ser revistos.
Uma equipa internacional liderada por Stephane Guilloteau do Laboratoire d´Astrophysique de Bordeaux, França, mediu a temperatura de enormes grãos de poeira que se encontram em torno da jovem estrela 2MASS J16281370-2431391 na região de formação estelar Rho Ophiuchi, a cerca de 400 anos-luz de distância da Terra.
Esta estrela encontra-se rodeada por um disco de gás e poeira — chamado disco protoplanetário, uma vez que se encontra na fase inicial da formação de um sistema planetário. Este disco é visto de perfil quando observado a partir da Terra e a sua aparência em imagens no visível levou a que se lhe desse o nome informal de Disco Voador.
Os astrónomos utilizaram o ALMA para observar o brilho emitido pelas moléculas de monóxido de carbono no disco da 2MASS J16281370-2431391. As imagens revelaram-se extremamente nítidas e descobriu-se algo estranho — em alguns casos o sinal recebido era negativo. Normalmente um sinal negativo é fisicamente impossível, mas neste caso existe uma explicação, que leva a uma conclusão surpreendente.
M82 X-2 is the first pulsating ultraluminous X-ray source discovered. The luminosity of these extreme pulsars, if
isotropic, implies an extreme mass transfer rate. An alternative is to assume a much lower mass transfer rate, but
with an apparent luminosity boosted by geometrical beaming. Only an independent measurement of the mass
transfer rate can help discriminate between these two scenarios. In this paper, we follow the orbit of the neutron star
for 7 yr, measure the decay of the orbit (P P orb orb 8 10 yr 6 1 · » - - - ), and argue that this orbital decay is driven by
extreme mass transfer of more than 150 times the mass transfer limit set by the Eddington luminosity. If this is true,
the mass available to the accretor is more than enough to justify its luminosity, with no need for beaming. This also
strongly favors models where the accretor is a highly magnetized neutron star.
Magnetic fields and relativistic electrons fill entire galaxy clusterSérgio Sacani
- The authors analyzed deep LOFAR radio observations of the galaxy cluster Abell 2255, detecting radio synchrotron emission distributed over an unprecedented scale of at least 5 megaparsecs, well beyond the cluster outskirts.
- This pervasive radio emission indicates that shocks and turbulence efficiently transfer kinetic energy into relativistic particles and magnetic fields throughout the cluster, including the periphery.
- The strength of the emission requires magnetic field energy densities at least 100 times higher than expected from simple compression of primordial fields, suggesting efficient dynamo action even in the cluster outskirts.
ALMA Observations of the Extraordinary Carina Pillars: A Complementary SampleSérgio Sacani
We present a study of six dusty and gaseous pillars (containing the HH 1004 and HH 1010 objects)
and globules (that contain the HH 666, HH 900, HH 1006, and HH 1066 objects) localized in the Carina
nebula using sensitive and high angular resolution (∼0.3′′) Atacama Large Millimeter/Sub-millimeter
Array (ALMA) observations. This is a more extensive study that the one presented in Cortes-Rangel
et al. (2020). As in this former study, we also analyzed the 1.3 mm continuum emission and C18O(2−1),
N2D+(3−2) and 12CO(2−1) spectral lines. These new observations revealed the molecular outflows
emanating from the pillars, the dusty envelopes+disks that are exciting them, and the extended HH
objects far from their respective pillars. We reveal that the masses of the disks+envelopes are in a
range of 0.02 to 0.38 M⊙, and those for the molecular outflows are of the order of 10−3 M⊙, which
suggests that their exciting sources might be low- or intermediate-mass protostars as already revealed
in recent studies at infrared and submillimeter bands. In the regions associated with the objects HH
900 and HH 1004, we report multiple millimeter continuum sources, from where several molecular
outflows emanate.
Bright radio emission_from_an_ultraluminous_stellar_mass_microquasar_in_m31Sérgio Sacani
1) A new ultraluminous X-ray source (ULX) was detected in the galaxy M31 with a peak X-ray luminosity exceeding 10^39 erg s^-1.
2) Radio observations found highly variable radio emission on timescales of minutes to days, indicating an extremely compact emission region.
3) The X-ray and radio properties of this source are consistent with stellar-mass black hole accretion near or above the Eddington limit, powered by a relativistic jet as seen in Galactic microquasars.
An elevation of 0.1 light-seconds for the optical jet base in an accreting Ga...Sérgio Sacani
Relativistic plasma jets are observed in many systems that
host accreting black holes. According to theory, coiled magnetic
fields close to the black hole accelerate and collimate the
plasma, leading to a jet being launched1–3. Isolating emission
from this acceleration and collimation zone is key to measuring
its size and understanding jet formation physics. But this
is challenging because emission from the jet base cannot
easily be disentangled from other accreting components. Here,
we show that rapid optical flux variations from an accreting
Galactic black-hole binary are delayed with respect to X-rays
radiated from close to the black hole by about 0.1 seconds, and
that this delayed signal appears together with a brightening
radio jet. The origin of these subsecond optical variations
has hitherto been controversial4–8. Not only does our work
strongly support a jet origin for the optical variations but it
also sets a characteristic elevation of ≲ 103 Schwarzschild
radii for the main inner optical emission zone above the black
hole9, constraining both internal shock10 and magnetohydrodynamic11
models. Similarities with blazars12,13 suggest that jet
structure and launching physics could potentially be unified
under mass-invariant models. Two of the best-studied jetted
black-hole binaries show very similar optical lags8,14,15, so this
size scale may be a defining feature of such systems.
Propagation of highly_efficient_star_formation_in_ngc7000Sérgio Sacani
This document summarizes a study of star formation in molecular clouds near the H II region NGC 7000. The authors surveyed NH3 and H2O maser emission toward the molecular cloud L935 located near NGC 7000. They identified five dense molecular clumps based on NH3 emission, which have similar gas temperatures but different levels of star formation activity. One clump located near the boundary of the H II region has a high star formation efficiency of 36-62%, suggesting triggered star formation due to its interaction with the expanding H II region.
This document summarizes a study examining the hypergiant star ρ Cassiopeiae. The researchers developed a model to explain ρ Cassiopeiae's variable mass loss rate, high microturbulent velocity, and Hα emission line profile using a stochastic field of shock waves in the star's atmosphere. Their model successfully reproduced the observed mass loss rate, microturbulent velocity, and aspects of the Hα profile using only one parameter - the maximum Mach number of shock waves in the atmosphere. The model indicates that thin, hot regions behind shock waves are responsible for the observed microturbulence and contribute to Hα emission.
The shadow _of_the_flying_saucer_a_very_low_temperature_for_large_dust_grainsSérgio Sacani
Os astrónomos usaram o ALMA e os telescópios do IRAM para fazer a primeira medição direta da temperatura dos grãos de poeira grandes situados nas regiões periféricas de um disco de formação planetária que se encontra em torno de uma estrela jovem. Ao observar de forma inovadora um objeto cujo nome informal é Disco Voador, os astrónomos descobriram que os grãos de poeira são muito mais frios do que o esperado: -266º Celsius. Este resultado surpreendente sugere que os modelos teóricos destes discos precisam de ser revistos.
Uma equipa internacional liderada por Stephane Guilloteau do Laboratoire d´Astrophysique de Bordeaux, França, mediu a temperatura de enormes grãos de poeira que se encontram em torno da jovem estrela 2MASS J16281370-2431391 na região de formação estelar Rho Ophiuchi, a cerca de 400 anos-luz de distância da Terra.
Esta estrela encontra-se rodeada por um disco de gás e poeira — chamado disco protoplanetário, uma vez que se encontra na fase inicial da formação de um sistema planetário. Este disco é visto de perfil quando observado a partir da Terra e a sua aparência em imagens no visível levou a que se lhe desse o nome informal de Disco Voador.
Os astrónomos utilizaram o ALMA para observar o brilho emitido pelas moléculas de monóxido de carbono no disco da 2MASS J16281370-2431391. As imagens revelaram-se extremamente nítidas e descobriu-se algo estranho — em alguns casos o sinal recebido era negativo. Normalmente um sinal negativo é fisicamente impossível, mas neste caso existe uma explicação, que leva a uma conclusão surpreendente.
M82 X-2 is the first pulsating ultraluminous X-ray source discovered. The luminosity of these extreme pulsars, if
isotropic, implies an extreme mass transfer rate. An alternative is to assume a much lower mass transfer rate, but
with an apparent luminosity boosted by geometrical beaming. Only an independent measurement of the mass
transfer rate can help discriminate between these two scenarios. In this paper, we follow the orbit of the neutron star
for 7 yr, measure the decay of the orbit (P P orb orb 8 10 yr 6 1 · » - - - ), and argue that this orbital decay is driven by
extreme mass transfer of more than 150 times the mass transfer limit set by the Eddington luminosity. If this is true,
the mass available to the accretor is more than enough to justify its luminosity, with no need for beaming. This also
strongly favors models where the accretor is a highly magnetized neutron star.
Magnetic fields and relativistic electrons fill entire galaxy clusterSérgio Sacani
- The authors analyzed deep LOFAR radio observations of the galaxy cluster Abell 2255, detecting radio synchrotron emission distributed over an unprecedented scale of at least 5 megaparsecs, well beyond the cluster outskirts.
- This pervasive radio emission indicates that shocks and turbulence efficiently transfer kinetic energy into relativistic particles and magnetic fields throughout the cluster, including the periphery.
- The strength of the emission requires magnetic field energy densities at least 100 times higher than expected from simple compression of primordial fields, suggesting efficient dynamo action even in the cluster outskirts.
ALMA Observations of the Extraordinary Carina Pillars: A Complementary SampleSérgio Sacani
We present a study of six dusty and gaseous pillars (containing the HH 1004 and HH 1010 objects)
and globules (that contain the HH 666, HH 900, HH 1006, and HH 1066 objects) localized in the Carina
nebula using sensitive and high angular resolution (∼0.3′′) Atacama Large Millimeter/Sub-millimeter
Array (ALMA) observations. This is a more extensive study that the one presented in Cortes-Rangel
et al. (2020). As in this former study, we also analyzed the 1.3 mm continuum emission and C18O(2−1),
N2D+(3−2) and 12CO(2−1) spectral lines. These new observations revealed the molecular outflows
emanating from the pillars, the dusty envelopes+disks that are exciting them, and the extended HH
objects far from their respective pillars. We reveal that the masses of the disks+envelopes are in a
range of 0.02 to 0.38 M⊙, and those for the molecular outflows are of the order of 10−3 M⊙, which
suggests that their exciting sources might be low- or intermediate-mass protostars as already revealed
in recent studies at infrared and submillimeter bands. In the regions associated with the objects HH
900 and HH 1004, we report multiple millimeter continuum sources, from where several molecular
outflows emanate.
An ultrahot gas-giant exoplanet with a stratosphereSérgio Sacani
Infrared radiation emitted from a planet contains information
about the chemical composition and vertical temperature profile
of its atmosphere1–3. If upper layers are cooler than lower layers,
molecular gases will produce absorption features in the planetary
thermal spectrum4,5
. Conversely, if there is a stratosphere—
where temperature increases with altitude—these molecular
features will be observed in emission6–8. It has been suggested that
stratospheres could form in highly irradiated exoplanets9,10, but
the extent to which this occurs is unresolved both theoretically11,12
and observationally3,13–15. A previous claim for the presence of a
stratosphere14 remains open to question, owing to the challenges
posed by the highly variable host star and the low spectral resolution
of the measurements3
. Here we report a near-infrared thermal
spectrum for the ultrahot gas giant WASP-121b, which has an
equilibrium temperature of approximately 2,500 kelvin. Water
is resolved in emission, providing a detection of an exoplanet
stratosphere at 5σ confidence. These observations imply that a
substantial fraction of incident stellar radiation is retained at high
altitudes in the atmosphere, possibly by absorbing chemical species
such as gaseous vanadium oxide and titanium oxide
Herschel far infrared_spectroscopy_of_the_galactic_centerSérgio Sacani
The document summarizes observations from the Herschel Space Observatory of the Galactic Center region, focusing on a spectral scan toward Sagittarius A*. Key findings include:
1) Strong emission from atomic fine structure lines and rotationally excited lines of molecules like CO, H2O and HCO+ are detected.
2) The excitation of the CO ladder is consistent with either a hot isothermal gas component at 103.1 K and 104 cm-3, or a distribution of warmer gas at higher densities, with most CO at 300 K.
3) The detected molecular features suggest heating is from a combination of UV irradiation and shocks in the gas, rather than very enhanced X-ray or cosmic
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
This document reports the discovery of a newly discovered optical Einstein ring (ER) called the "Canarias Einstein Ring". It was discovered serendipitously in imaging data from the Dark Energy Camera. Follow-up spectroscopy with the Gran Telescopio CANARIAS confirmed the nature of the system, with the lens being an early-type galaxy at a redshift of z=0.581 and the source being a starburst galaxy at z=1.165. Analysis of the system determined the Einstein radius to be 2.16 arcseconds and the total enclosed mass producing the lensing effect to be 1.86 ± 0.23 × 1012 solar masses.
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
A dust-enshrouded tidal disruption event with a resolved radio jet in a galax...Sérgio Sacani
Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the
gravitational field of a supermassive black hole (SMBH). We have observed a transient source in the
western nucleus of the merging galaxy pair Arp 299 that radiated >1.5 × 1052 erg in the infrared and radio
but was not luminous at optical or x-ray wavelengths. We interpret this as a TDE with much of its emission
reradiated at infrared wavelengths by dust. Efficient reprocessing by dense gas and dust may explain the
difference between theoretical predictions and observed luminosities of TDEs. The radio observations
resolve an expanding and decelerating jet, probing the jet formation and evolution around a SMBH.
Dust in the_polar_region_as_a_major_contributor_to_the_infrared_emission_of_a...Sérgio Sacani
The mid-infrared emission of the active galactic nucleus NGC 3783 was observed using interferometry over multiple epochs, providing dense coverage of position angles and baselines. The emission was found to be strongly elongated along a position angle of -52 degrees, closely aligned with the polar axis orientation of -45 degrees. The half-light radii were measured to be 20.0 mas by 6.7 mas, corresponding to an axis ratio of 3:1. This implies that 60-90% of the 8-13 micron emission is from the polar-elongated component. The observations support a scenario where the majority of mid-infrared emission in Seyfert galaxies originates from a dusty wind in the polar region,
Evidence of a plume on Europa from Galileo magnetic and plasma wave signaturesSérgio Sacani
The icy surface of Jupiter’s moon, Europa, is thought to lie
on top of a global ocean1–4. Signatures in some Hubble Space
Telescope images have been associated with putative water
plumes rising above Europa’s surface5,6, providing support for
the ocean theory. However, all telescopic detections reported
were made at the limit of sensitivity of the data5–7
, thereby calling
for a search for plume signatures in in-situ measurements.
Here, we report in-situ evidence of a plume on Europa from
the magnetic field and plasma wave observations acquired on
Galileo’s closest encounter with the moon. During this flyby,
which dropped below 400 km altitude, the magnetometer8
recorded an approximately 1,000-kilometre-scale field rotation
and a decrease of over 200 nT in field magnitude, and
the Plasma Wave Spectrometer9 registered intense localized
wave emissions indicative of a brief but substantial increase
in plasma density. We show that the location, duration and
variations of the magnetic field and plasma wave measurements
are consistent with the interaction of Jupiter’s corotating
plasma with Europa if a plume with characteristics inferred
from Hubble images were erupting from the region of Europa’s
thermal anomalies. These results provide strong independent
evidence of the presence of plumes at Europa.
Multimessenger observations of a flaring blazar coincident with high-energy n...Sérgio Sacani
Neutrinos are tracers of
cosmic-ray acceleration: electrically neutral
and traveling at nearly the speed of light, they
can escape the densest environments and may
be traced back to their source of origin. Highenergy
neutrinos are expected to be produced
in blazars: intense extragalactic radio, optical,
x-ray, and,in some cases, g-ray sources
characterized by relativistic jets of
plasma pointing close to our line of
sight. Blazars are among the most
powerful objects in the Universe and
are widely speculated to be sources
of high-energy cosmic rays. These cosmic
rays generate high-energy neutrinos
and g-rays, which are produced
when the cosmic rays accelerated in
the jet interact with nearby gas or
photons. On 22 September 2017, the
cubic-kilometer IceCube Neutrino
Observatory detected a ~290-TeV
neutrino from a direction consistent
with the flaring g-ray blazar TXS
0506+056. We report the details of
this observation and the results of a
multiwavelength follow-up campaign
Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U...Sérgio Sacani
During the formation and evolution of the Solar System, significant
numbers of cometary and asteroidal bodies were
ejected into interstellar space1,2. It is reasonable to expect that
the same happened for planetary systems other than our own.
Detection of such interstellar objects would allow us to probe
the planetesimal formation processes around other stars, possibly
together with the effects of long-term exposure to the
interstellar medium. 1I/2017 U1 ‘Oumuamua is the first known
interstellar object, discovered by the Pan-STARRS1 telescope
in October 2017 (ref. 3). The discovery epoch photometry
implies a highly elongated body with radii of ~ 200 × 20 m
when a comet-like geometric albedo of 0.04 is assumed. The
observable interstellar object population is expected to be
dominated by comet-like bodies in agreement with our spectra,
yet the reported inactivity of 'Oumuamua implies a lack
of surface ice. Here, we report spectroscopic characterization
of ‘Oumuamua, finding it to be variable with time but similar
to organically rich surfaces found in the outer Solar System.
We show that this is consistent with predictions of an insulating
mantle produced by long-term cosmic ray exposure4.
An internal icy composition cannot therefore be ruled out by
the lack of activity, even though ‘Oumuamua passed within
0.25 au of the Sun.
A density cusp of quiescent X-ray binaries in the central parsec of the GalaxySérgio Sacani
The existence of a ‘density cusp’1,2—a localized increase in
number—of stellar-mass black holes near a supermassive black
hole is a fundamental prediction of galactic stellar dynamics3
. The
best place to detect such a cusp is in the Galactic Centre, where
the nearest supermassive black hole, Sagittarius A*, resides. As
many as 20,000 black holes are predicted to settle into the central
parsec of the Galaxy as a result of dynamical friction3–5; however,
so far no density cusp of black holes has been detected. Low-mass
X-ray binary systems that contain a stellar-mass black hole are
natural tracers of isolated black holes. Here we report observations
of a dozen quiescent X-ray binaries in a density cusp within one
parsec of Sagittarius A*. The lower-energy emission spectra that
we observed in these binaries is distinct from the higher-energy
spectra associated with the population of accreting white dwarfs that
dominates the central eight parsecs of the Galaxy6
. The properties
of these X-ray binaries, in particular their spatial distribution and
luminosity function, suggest the existence of hundreds of binary
systems in the central parsec of the Galaxy and many more isolated
black holes. We cannot rule out a contribution to the observed
emission from a population (of up to about one-half the number of
X-ray binaries) of rotationally powered, millisecond pulsars. The
spatial distribution of the binary systems is a relic of their formation
history, either in the stellar disk around Sagittarius A* (ref. 7) or
through in-fall from globular clusters, and constrains the number
density of sources in the modelling of gravitational waves from
massive stellar remnants8,9
, such as neutron stars and black holes.
This document proposes a new method to test the isotropy of ultrahigh energy cosmic ray arrival directions. The method analyzes how cosmic rays cluster together into groups as the maximum angular separation between events is increased. It characterizes the clustering process through various observables like the number and sizes of clusters. The method is applied to real data from the Pierre Auger Observatory. The strongest signal of anisotropy is found for events above 56.74 EeV with an angular scale of 4 degrees, rejecting isotropy at nearly 90% confidence level.
A 300 parsec-long jet-inflated bubble around a powerful microquasar in the ga...Sérgio Sacani
This document summarizes the discovery of a 300-parsec-long jet-inflated bubble around a powerful microquasar in the galaxy NGC 7793. Chandra X-ray observations revealed an aligned triple X-ray source within the optical nebula S26, consisting of a central core and two hot spots, interpreted as the core of the X-ray binary and where the jets interact with the ambient medium. Spectral analysis found the core has a hard power-law spectrum, while the hot spots have softer thermal plasma emission. The morphology and properties of S26 resemble those of a powerful FRII-type active galaxy, indicating it is powered by collimated jets with mechanical luminosity of ~10^40 er
Radio continum emission_of_35_edge_on_galaxies_observed_with_the_vlaSérgio Sacani
Usando um dos maiores rádio observatórios do mundo, o Very Large Array do National Radio Astronomy, um grupo de astrônomos descobriram que os halos ao redor dos discos das galáxias espirais são muito mais comuns do que se pensava anteriormente.
A equipe, dirigida pela Dra. Judith Irwin, da Universidade de Queens, em Kingston, ON, Canadá, observou 35 galáxias espirais próximas de lado, de 11 a 137 milhões de anos-luz de distância da Terra.
As galáxias espirais, como a nossa própria Via Láctea ou a famosa Galáxia de Andrômeda, possuem uma vasta maioria de suas estrelas, gás, e poeira num disco plano em rotação com braços espirais. A maior parte da luz e das ondas de rádio observadas com telescópios veem de objetos localizados nesse disco.
“Nós sabíamos antes que alguns halos existiam, mas, usando o poder total do VLA atualizado e o poder total de algumas técnicas de processamento de imagens, nós descobrimos que esses halos são muito mais comuns entre as galáxias espirais do que nós pensávamos antes”, explicou a Dra. Irwin.
A thirty-four billion solar mass black hole in SMSS J2157–3602, the most lumi...Sérgio Sacani
From near-infrared spectroscopic measurements of the Mg II emission line doublet, we estimate the black hole (BH) mass of the quasar, SMSS J215728.21–360215.1, as being (3.4 ± 0.6) × 1010 M⊙ and refine the redshift of the quasar to be z = 4.692. SMSS J2157 is the most luminous known quasar, with a 3000 Å luminosity of (4.7 ± 0.5) × 1047 erg s−1 and an estimated bolometric luminosity of 1.6 × 1048 erg s−1 , yet its Eddington ratio is only ∼0.4. Thus, the high luminosity of this quasar is a consequence of its extremely large BH – one of the most massive BHs at z > 4.
Thermonuclear explosions on neutron stars reveal the speed of their jetsSérgio Sacani
Relativistic jets are observed from accreting and cataclysmic transients throughout
the Universe, and have a profound impact on their surroundings1,2
. Despite their
importance, their launch mechanism is not known. For accreting neutron stars, the
speed of their compact jets can reveal whether the jets are powered by magnetic felds
anchored in the accretion fow3
or in the star itself 4,5
, but so far no such measurements
exist. These objects can show bright explosions on their surface due to unstable
thermonuclear burning of recently accreted material, called type-I X-ray bursts6
,
during which the mass-accretion rate increases7–9
. Here, we report on bright fares in
the jet emission for a few minutes after each X-ray burst, attributed to the increased
accretion rate. With these fares, we measure the speed of a neutron star compact jet
to be v c = 0.38−0.08
+0.11 , much slower than those from black holes at similar luminosities.
This discovery provides a powerful new tool in which we can determine the role that
individual system properties have on the jet speed, revealing the dominant jet
launching mechanism.
The deep blue_color_of_hd189733b_albedo_measurements_with_hst_stis_at_visible...Sérgio Sacani
The document summarizes a study that measured the geometric albedo of the exoplanet HD 189733b across visible wavelengths using Hubble Space Telescope observations. It found an albedo of 0.40 ± 0.12 at 290-450 nm that decreased to below 0.12 at 450-570 nm, suggesting optically thick clouds reflecting light at shorter wavelengths and sodium absorption suppressing reflection beyond 450 nm. This wavelength-dependent albedo implies HD 189733b would appear deep blue in color at visible wavelengths.
Detectcion of noble_gas_molecular_ion_arh_in_the_crab_nebulaSérgio Sacani
Scientists detected emission lines from the ionized argon hydride (36ArH+) molecule in spectra of the Crab Nebula obtained with the Herschel Space Observatory. The detection of 36ArH+ confirms that argon originated from explosive nucleosynthesis during the core-collapse supernova that created the Crab Nebula. The likely excitation mechanism is electron collisions in partially ionized regions with electron densities of a few hundred per cubic centimeter. This is the first detection of a noble gas molecule in space.
A Tectonic Origin for the Largest Marsquake Observed by InSightSérgio Sacani
The S1222a marsquake detected by InSight on 4 May 2022 was the largest of the mission, at 𝐴𝐴𝐴𝐴𝐴𝐴𝑀𝑀𝑤𝑤 4.7. Given its resemblance to two other large seismic events (S1000a and S1094b), which were associated with the formation of fresh craters, we undertook a search for a fresh crater associated with S1222a. Such a crater would be expected to be ∼300 m in diameter and have a blast zone on the order of 180 km across. Orbital images were targeted and searched as part of an international, multi-mission effort. Comprehensive analysis of the area using low- and medium-resolution images reveals no relevant transient atmospheric phenomena and no fresh blast zone. High-resolution coverage of the epicentral area from most spacecraft are more limited, but no fresh crater or other evidence of a new impact have been identified in those images either. We thus conclude that the S1222a event was highly likely of tectonic origin
Detection of Radio Emission from FireballsCarlos Bella
This document summarizes the detection of radio emissions from fireballs (very bright meteors) using the Long Wavelength Array radio telescope. A search of over 11,000 hours of all-sky radio images found 49 long-duration radio transients. Ten of these transients correlated spatially and temporally with fireballs detected by an optical meteor monitoring network. This provides evidence that fireballs emit previously undiscovered low frequency radio pulses. Further analysis found characteristics inconsistent with expected radio reflections from meteor trails, suggesting a non-thermal radio emission mechanism from the fireballs. This identifies a new class of natural radio transients and provides a new probe to study meteor physics.
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
Mais conteúdo relacionado
Semelhante a Detection of the infrared aurora at Uranus with Keck-NIRSPEC
An ultrahot gas-giant exoplanet with a stratosphereSérgio Sacani
Infrared radiation emitted from a planet contains information
about the chemical composition and vertical temperature profile
of its atmosphere1–3. If upper layers are cooler than lower layers,
molecular gases will produce absorption features in the planetary
thermal spectrum4,5
. Conversely, if there is a stratosphere—
where temperature increases with altitude—these molecular
features will be observed in emission6–8. It has been suggested that
stratospheres could form in highly irradiated exoplanets9,10, but
the extent to which this occurs is unresolved both theoretically11,12
and observationally3,13–15. A previous claim for the presence of a
stratosphere14 remains open to question, owing to the challenges
posed by the highly variable host star and the low spectral resolution
of the measurements3
. Here we report a near-infrared thermal
spectrum for the ultrahot gas giant WASP-121b, which has an
equilibrium temperature of approximately 2,500 kelvin. Water
is resolved in emission, providing a detection of an exoplanet
stratosphere at 5σ confidence. These observations imply that a
substantial fraction of incident stellar radiation is retained at high
altitudes in the atmosphere, possibly by absorbing chemical species
such as gaseous vanadium oxide and titanium oxide
Herschel far infrared_spectroscopy_of_the_galactic_centerSérgio Sacani
The document summarizes observations from the Herschel Space Observatory of the Galactic Center region, focusing on a spectral scan toward Sagittarius A*. Key findings include:
1) Strong emission from atomic fine structure lines and rotationally excited lines of molecules like CO, H2O and HCO+ are detected.
2) The excitation of the CO ladder is consistent with either a hot isothermal gas component at 103.1 K and 104 cm-3, or a distribution of warmer gas at higher densities, with most CO at 300 K.
3) The detected molecular features suggest heating is from a combination of UV irradiation and shocks in the gas, rather than very enhanced X-ray or cosmic
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
This document reports the discovery of a newly discovered optical Einstein ring (ER) called the "Canarias Einstein Ring". It was discovered serendipitously in imaging data from the Dark Energy Camera. Follow-up spectroscopy with the Gran Telescopio CANARIAS confirmed the nature of the system, with the lens being an early-type galaxy at a redshift of z=0.581 and the source being a starburst galaxy at z=1.165. Analysis of the system determined the Einstein radius to be 2.16 arcseconds and the total enclosed mass producing the lensing effect to be 1.86 ± 0.23 × 1012 solar masses.
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
A dust-enshrouded tidal disruption event with a resolved radio jet in a galax...Sérgio Sacani
Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the
gravitational field of a supermassive black hole (SMBH). We have observed a transient source in the
western nucleus of the merging galaxy pair Arp 299 that radiated >1.5 × 1052 erg in the infrared and radio
but was not luminous at optical or x-ray wavelengths. We interpret this as a TDE with much of its emission
reradiated at infrared wavelengths by dust. Efficient reprocessing by dense gas and dust may explain the
difference between theoretical predictions and observed luminosities of TDEs. The radio observations
resolve an expanding and decelerating jet, probing the jet formation and evolution around a SMBH.
Dust in the_polar_region_as_a_major_contributor_to_the_infrared_emission_of_a...Sérgio Sacani
The mid-infrared emission of the active galactic nucleus NGC 3783 was observed using interferometry over multiple epochs, providing dense coverage of position angles and baselines. The emission was found to be strongly elongated along a position angle of -52 degrees, closely aligned with the polar axis orientation of -45 degrees. The half-light radii were measured to be 20.0 mas by 6.7 mas, corresponding to an axis ratio of 3:1. This implies that 60-90% of the 8-13 micron emission is from the polar-elongated component. The observations support a scenario where the majority of mid-infrared emission in Seyfert galaxies originates from a dusty wind in the polar region,
Evidence of a plume on Europa from Galileo magnetic and plasma wave signaturesSérgio Sacani
The icy surface of Jupiter’s moon, Europa, is thought to lie
on top of a global ocean1–4. Signatures in some Hubble Space
Telescope images have been associated with putative water
plumes rising above Europa’s surface5,6, providing support for
the ocean theory. However, all telescopic detections reported
were made at the limit of sensitivity of the data5–7
, thereby calling
for a search for plume signatures in in-situ measurements.
Here, we report in-situ evidence of a plume on Europa from
the magnetic field and plasma wave observations acquired on
Galileo’s closest encounter with the moon. During this flyby,
which dropped below 400 km altitude, the magnetometer8
recorded an approximately 1,000-kilometre-scale field rotation
and a decrease of over 200 nT in field magnitude, and
the Plasma Wave Spectrometer9 registered intense localized
wave emissions indicative of a brief but substantial increase
in plasma density. We show that the location, duration and
variations of the magnetic field and plasma wave measurements
are consistent with the interaction of Jupiter’s corotating
plasma with Europa if a plume with characteristics inferred
from Hubble images were erupting from the region of Europa’s
thermal anomalies. These results provide strong independent
evidence of the presence of plumes at Europa.
Multimessenger observations of a flaring blazar coincident with high-energy n...Sérgio Sacani
Neutrinos are tracers of
cosmic-ray acceleration: electrically neutral
and traveling at nearly the speed of light, they
can escape the densest environments and may
be traced back to their source of origin. Highenergy
neutrinos are expected to be produced
in blazars: intense extragalactic radio, optical,
x-ray, and,in some cases, g-ray sources
characterized by relativistic jets of
plasma pointing close to our line of
sight. Blazars are among the most
powerful objects in the Universe and
are widely speculated to be sources
of high-energy cosmic rays. These cosmic
rays generate high-energy neutrinos
and g-rays, which are produced
when the cosmic rays accelerated in
the jet interact with nearby gas or
photons. On 22 September 2017, the
cubic-kilometer IceCube Neutrino
Observatory detected a ~290-TeV
neutrino from a direction consistent
with the flaring g-ray blazar TXS
0506+056. We report the details of
this observation and the results of a
multiwavelength follow-up campaign
Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U...Sérgio Sacani
During the formation and evolution of the Solar System, significant
numbers of cometary and asteroidal bodies were
ejected into interstellar space1,2. It is reasonable to expect that
the same happened for planetary systems other than our own.
Detection of such interstellar objects would allow us to probe
the planetesimal formation processes around other stars, possibly
together with the effects of long-term exposure to the
interstellar medium. 1I/2017 U1 ‘Oumuamua is the first known
interstellar object, discovered by the Pan-STARRS1 telescope
in October 2017 (ref. 3). The discovery epoch photometry
implies a highly elongated body with radii of ~ 200 × 20 m
when a comet-like geometric albedo of 0.04 is assumed. The
observable interstellar object population is expected to be
dominated by comet-like bodies in agreement with our spectra,
yet the reported inactivity of 'Oumuamua implies a lack
of surface ice. Here, we report spectroscopic characterization
of ‘Oumuamua, finding it to be variable with time but similar
to organically rich surfaces found in the outer Solar System.
We show that this is consistent with predictions of an insulating
mantle produced by long-term cosmic ray exposure4.
An internal icy composition cannot therefore be ruled out by
the lack of activity, even though ‘Oumuamua passed within
0.25 au of the Sun.
A density cusp of quiescent X-ray binaries in the central parsec of the GalaxySérgio Sacani
The existence of a ‘density cusp’1,2—a localized increase in
number—of stellar-mass black holes near a supermassive black
hole is a fundamental prediction of galactic stellar dynamics3
. The
best place to detect such a cusp is in the Galactic Centre, where
the nearest supermassive black hole, Sagittarius A*, resides. As
many as 20,000 black holes are predicted to settle into the central
parsec of the Galaxy as a result of dynamical friction3–5; however,
so far no density cusp of black holes has been detected. Low-mass
X-ray binary systems that contain a stellar-mass black hole are
natural tracers of isolated black holes. Here we report observations
of a dozen quiescent X-ray binaries in a density cusp within one
parsec of Sagittarius A*. The lower-energy emission spectra that
we observed in these binaries is distinct from the higher-energy
spectra associated with the population of accreting white dwarfs that
dominates the central eight parsecs of the Galaxy6
. The properties
of these X-ray binaries, in particular their spatial distribution and
luminosity function, suggest the existence of hundreds of binary
systems in the central parsec of the Galaxy and many more isolated
black holes. We cannot rule out a contribution to the observed
emission from a population (of up to about one-half the number of
X-ray binaries) of rotationally powered, millisecond pulsars. The
spatial distribution of the binary systems is a relic of their formation
history, either in the stellar disk around Sagittarius A* (ref. 7) or
through in-fall from globular clusters, and constrains the number
density of sources in the modelling of gravitational waves from
massive stellar remnants8,9
, such as neutron stars and black holes.
This document proposes a new method to test the isotropy of ultrahigh energy cosmic ray arrival directions. The method analyzes how cosmic rays cluster together into groups as the maximum angular separation between events is increased. It characterizes the clustering process through various observables like the number and sizes of clusters. The method is applied to real data from the Pierre Auger Observatory. The strongest signal of anisotropy is found for events above 56.74 EeV with an angular scale of 4 degrees, rejecting isotropy at nearly 90% confidence level.
A 300 parsec-long jet-inflated bubble around a powerful microquasar in the ga...Sérgio Sacani
This document summarizes the discovery of a 300-parsec-long jet-inflated bubble around a powerful microquasar in the galaxy NGC 7793. Chandra X-ray observations revealed an aligned triple X-ray source within the optical nebula S26, consisting of a central core and two hot spots, interpreted as the core of the X-ray binary and where the jets interact with the ambient medium. Spectral analysis found the core has a hard power-law spectrum, while the hot spots have softer thermal plasma emission. The morphology and properties of S26 resemble those of a powerful FRII-type active galaxy, indicating it is powered by collimated jets with mechanical luminosity of ~10^40 er
Radio continum emission_of_35_edge_on_galaxies_observed_with_the_vlaSérgio Sacani
Usando um dos maiores rádio observatórios do mundo, o Very Large Array do National Radio Astronomy, um grupo de astrônomos descobriram que os halos ao redor dos discos das galáxias espirais são muito mais comuns do que se pensava anteriormente.
A equipe, dirigida pela Dra. Judith Irwin, da Universidade de Queens, em Kingston, ON, Canadá, observou 35 galáxias espirais próximas de lado, de 11 a 137 milhões de anos-luz de distância da Terra.
As galáxias espirais, como a nossa própria Via Láctea ou a famosa Galáxia de Andrômeda, possuem uma vasta maioria de suas estrelas, gás, e poeira num disco plano em rotação com braços espirais. A maior parte da luz e das ondas de rádio observadas com telescópios veem de objetos localizados nesse disco.
“Nós sabíamos antes que alguns halos existiam, mas, usando o poder total do VLA atualizado e o poder total de algumas técnicas de processamento de imagens, nós descobrimos que esses halos são muito mais comuns entre as galáxias espirais do que nós pensávamos antes”, explicou a Dra. Irwin.
A thirty-four billion solar mass black hole in SMSS J2157–3602, the most lumi...Sérgio Sacani
From near-infrared spectroscopic measurements of the Mg II emission line doublet, we estimate the black hole (BH) mass of the quasar, SMSS J215728.21–360215.1, as being (3.4 ± 0.6) × 1010 M⊙ and refine the redshift of the quasar to be z = 4.692. SMSS J2157 is the most luminous known quasar, with a 3000 Å luminosity of (4.7 ± 0.5) × 1047 erg s−1 and an estimated bolometric luminosity of 1.6 × 1048 erg s−1 , yet its Eddington ratio is only ∼0.4. Thus, the high luminosity of this quasar is a consequence of its extremely large BH – one of the most massive BHs at z > 4.
Thermonuclear explosions on neutron stars reveal the speed of their jetsSérgio Sacani
Relativistic jets are observed from accreting and cataclysmic transients throughout
the Universe, and have a profound impact on their surroundings1,2
. Despite their
importance, their launch mechanism is not known. For accreting neutron stars, the
speed of their compact jets can reveal whether the jets are powered by magnetic felds
anchored in the accretion fow3
or in the star itself 4,5
, but so far no such measurements
exist. These objects can show bright explosions on their surface due to unstable
thermonuclear burning of recently accreted material, called type-I X-ray bursts6
,
during which the mass-accretion rate increases7–9
. Here, we report on bright fares in
the jet emission for a few minutes after each X-ray burst, attributed to the increased
accretion rate. With these fares, we measure the speed of a neutron star compact jet
to be v c = 0.38−0.08
+0.11 , much slower than those from black holes at similar luminosities.
This discovery provides a powerful new tool in which we can determine the role that
individual system properties have on the jet speed, revealing the dominant jet
launching mechanism.
The deep blue_color_of_hd189733b_albedo_measurements_with_hst_stis_at_visible...Sérgio Sacani
The document summarizes a study that measured the geometric albedo of the exoplanet HD 189733b across visible wavelengths using Hubble Space Telescope observations. It found an albedo of 0.40 ± 0.12 at 290-450 nm that decreased to below 0.12 at 450-570 nm, suggesting optically thick clouds reflecting light at shorter wavelengths and sodium absorption suppressing reflection beyond 450 nm. This wavelength-dependent albedo implies HD 189733b would appear deep blue in color at visible wavelengths.
Detectcion of noble_gas_molecular_ion_arh_in_the_crab_nebulaSérgio Sacani
Scientists detected emission lines from the ionized argon hydride (36ArH+) molecule in spectra of the Crab Nebula obtained with the Herschel Space Observatory. The detection of 36ArH+ confirms that argon originated from explosive nucleosynthesis during the core-collapse supernova that created the Crab Nebula. The likely excitation mechanism is electron collisions in partially ionized regions with electron densities of a few hundred per cubic centimeter. This is the first detection of a noble gas molecule in space.
A Tectonic Origin for the Largest Marsquake Observed by InSightSérgio Sacani
The S1222a marsquake detected by InSight on 4 May 2022 was the largest of the mission, at 𝐴𝐴𝐴𝐴𝐴𝐴𝑀𝑀𝑤𝑤 4.7. Given its resemblance to two other large seismic events (S1000a and S1094b), which were associated with the formation of fresh craters, we undertook a search for a fresh crater associated with S1222a. Such a crater would be expected to be ∼300 m in diameter and have a blast zone on the order of 180 km across. Orbital images were targeted and searched as part of an international, multi-mission effort. Comprehensive analysis of the area using low- and medium-resolution images reveals no relevant transient atmospheric phenomena and no fresh blast zone. High-resolution coverage of the epicentral area from most spacecraft are more limited, but no fresh crater or other evidence of a new impact have been identified in those images either. We thus conclude that the S1222a event was highly likely of tectonic origin
Detection of Radio Emission from FireballsCarlos Bella
This document summarizes the detection of radio emissions from fireballs (very bright meteors) using the Long Wavelength Array radio telescope. A search of over 11,000 hours of all-sky radio images found 49 long-duration radio transients. Ten of these transients correlated spatially and temporally with fireballs detected by an optical meteor monitoring network. This provides evidence that fireballs emit previously undiscovered low frequency radio pulses. Further analysis found characteristics inconsistent with expected radio reflections from meteor trails, suggesting a non-thermal radio emission mechanism from the fireballs. This identifies a new class of natural radio transients and provides a new probe to study meteor physics.
Semelhante a Detection of the infrared aurora at Uranus with Keck-NIRSPEC (20)
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
BIRDS DIVERSITY OF SOOTEA BISWANATH ASSAM.ppt.pptxgoluk9330
Ahota Beel, nestled in Sootea Biswanath Assam , is celebrated for its extraordinary diversity of bird species. This wetland sanctuary supports a myriad of avian residents and migrants alike. Visitors can admire the elegant flights of migratory species such as the Northern Pintail and Eurasian Wigeon, alongside resident birds including the Asian Openbill and Pheasant-tailed Jacana. With its tranquil scenery and varied habitats, Ahota Beel offers a perfect haven for birdwatchers to appreciate and study the vibrant birdlife that thrives in this natural refuge.
Sexuality - Issues, Attitude and Behaviour - Applied Social Psychology - Psyc...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdfSelcen Ozturkcan
Ozturkcan, S., Berndt, A., & Angelakis, A. (2024). Mending clothing to support sustainable fashion. Presented at the 31st Annual Conference by the Consortium for International Marketing Research (CIMaR), 10-13 Jun 2024, University of Gävle, Sweden.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
TOPIC OF DISCUSSION: CENTRIFUGATION SLIDESHARE.pptxshubhijain836
Centrifugation is a powerful technique used in laboratories to separate components of a heterogeneous mixture based on their density. This process utilizes centrifugal force to rapidly spin samples, causing denser particles to migrate outward more quickly than lighter ones. As a result, distinct layers form within the sample tube, allowing for easy isolation and purification of target substances.
TOPIC OF DISCUSSION: CENTRIFUGATION SLIDESHARE.pptx
Detection of the infrared aurora at Uranus with Keck-NIRSPEC
1. Nature Astronomy
natureastronomy
https://doi.org/10.1038/s41550-023-02096-5
Article
DetectionoftheinfraredauroraatUranus
withKeck-NIRSPEC
Emma M. Thomas 1
, Henrik Melin 1
, Tom S. Stallard 2
,
Mohammad N. Chowdhury 1
, Ruoyan Wang 1
, Katie Knowles 2
&
Steve Miller3
Near-infrared(NIR)-wavelengthobservationsofUranushavebeenunable
tolocateanyinfraredaurorae,despitemanyattemptstodososincethe
1990s.WhileatJupiterandSaturn,NIRinvestigationshaveredefinedour
understandingofmagnetosphere–ionosphere–thermospherecoupling,the
lackofNIRauroraldetectionatUranusmeansthatwehavelacked awindow
throughwhichtostudytheseprocessesatUranus.HerewepresentNIR
UranianobservationswiththeKeckIItelescopetakenonthe5September
2006anddetectenhancedH3
+
emissions.Analysingtemperaturesand
columndensities,weidentifyan88%increaseinlocalizedH3
+
column
density,withnosignificanttemperatureincreases,consistentwithauroral
activitygeneratingincreasedionization.Bycomparingthesestructures
againsttheQ3
mp
magnetic-fieldmodelandtheVoyager2ultraviolet
observations,wesuggestthattheseregionsmakeupsectionsofthe
northernaurora.
One of the most unusual aspects of Uranus is its magnetic field, off
centredbyathirdoftheplanet’sradiusandtilted59°fromtheplanet’s
rotationalaxis1
.Withtheplanetaryrotationalaxisalsotiltedby98°,we
are presented with a truly distinctive magnetosphere. The only flyby
oftheplanetwasmadebyVoyagerIIin1986,wherethedatapresented
more questions than answers. Aurorae, presumably created by inter-
actions between Uranus’s magnetosphere and ionosphere, were first
simultaneously detected by several instruments onboard Voyager II.
Both radio (UKR) and ultraviolet (UV) emissions have shown auroral
morphologies that are very different from those seen at Jupiter and
Saturnandprovidethefoundationforauroralemissioncomparisons2–4
.
Investigations into Uranus’s aurora have continued with the Hubble
SpaceTelescope(HST)5–8
.Inthesestudies,15UVauroralemissionswere
identified:9southernauroraand6northernauroraemissions,largely
consistentwithpulsedcuspauroraeandobservedtoemitconjugately.
Inthesepreviousinvestigations,thesolar-windconditionswerefound
togreatlyaffecttheUranianaurorae,whereVoyagerIIrevealedacor-
relation between active solar-wind periods and UKR activity9
, with
HST data showing positive detections (~25%) of UV auroral emissions
thatcoincidedwithmodelledpeaksinsolar-windactivity5–8
.Itisnoted
that one UKR component (known as n-smooth) observed by ref. 10,
originatesfromclosetothemagneticequatorat2–3 RU andwashence
not considered auroral.
NIRemissionsfromH3
+
(amolecularion)havebeenfundamental
in developing our understanding of the aurorae at Jupiter and Sat-
urn11–21
.H3
+
wasfirstdiscoveredatUranusin1992(ref.22),andhasbeen
frequently analysed to characterize the ionosphere and understand
seasonal and temporal changes therein. For 30 years, a continuous
effort was made to document an infrared aurorae at Uranus14,23–26
. In
ref. 23, a 20% variation in H3
+
emissions was tentatively attributed to
auroralprocessesbutduetothelowsignal-to-noiseratio,itcouldnot
be confirmed whether these increases were auroral. In ref. 26, a local-
izedH3
+
emissionpeakwasobservedonthedawnsidelimbofUranus.
Its location aligned with the southern aurorae latitudes; however,
owingtotimeconstraints,thefeaturecouldnotbetrackedandremains
unconfirmed.Fromhereon,whendiscussingthegeometryofUranus,
werefertotheUranianlongitudecoordinatesystem(ULS)presented
byref.1.Inaddition,theexactlongitudeofUranusduringobservations
isunknownowingtothe±0.01 hrotationalperioduncertainty;hence,
thelongitudeatUranusiscompletelylostin~3.4 Earthyears.
Received: 2 December 2021
Accepted: 6 September 2023
Published online: xx xx xxxx
Check for updates
1
School of Physics and Astronomy, University of Leicester, Leicester, UK. 2
Department of Mathematics, Physics and Electrical Engineering, Northumbria
University, Newcastle upon Tyne, UK. 3
Department of Physics and Astronomy, University College London, London, UK. e-mail: emt18@leicester.ac.uk
2. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02096-5
Thefinalfittedspectraprovideintensityvaluesthatarethenmapped
acrossUranusasisshownwiththeQ(1,0−
)emissionline(withthehigh-
estsignal-to-noiseratio;Fig.2a),H3
+
totalemission(Fig.2b),tempera-
tures (Fig. 2c) and H3
+
column density (Fig. 2d). The respective error
mapsareshowninExtendedDataFig.2a–d.
In Fig. 2a,b, the H3
+
emission intensity varies with local time. To
confirmthesourceoftheseenhancements,wedefinethreeregionsof
interestthatarealgorithmicallydistinct:the‘enhanced’regionwhere
theemissionsarebrighterthanthemeanplusonestandarddeviation
(shown in solid black lines but not shaded); the ‘dim’ region where
emissions are below the mean emission (shaded with dots); and the
‘intermediate’ region where emissions are brighter than the mean,
but within a standard deviation of that mean (shaded by diagonal
lines).ThemeansandstandarddeviationsforFig.2a,b,dpresentedin
Table1aretheresultofsubtractingeachpixelbyitsuncertainty(seen
in Extended Data Fig. 2). The resulting datasets are hence minimized,
meaningpixelsintheenhancedregionarestatisticallysignificant.
In Fig. 2a, the enhanced regions show intriguing structures, the
first, which is smaller, between 26° S and 59° S and from 18° to 28°
longitude(E1).Thesecondareaextendsbetween15° Nand75 °Nfrom
100° and 143° longitude with two smaller emission spots between
10° Nand0°andbetween10° Sand20° Sovera108°to117°longitude
range, which we refer to as E2. Table 1 summarizes the mean values of
Q(1,0−
) intensities, along with mean values for temperature, column
density and total H3
+
emission. Comparing the dim region’s mean
Q(1,0−
)intensity(0.472 ± 0.086 μW m−2
sr−1
)withthatoftheenhanced
region (0.723 ± 0.010 μW m−2
sr−1
and 0.716 ± 0.009 μW m−2
sr−1
), we
finda27%to90%enhancement.
Figure 2b shows the total H3
+
emission, which is the combined
intensity from all H3
+
emission lines in this investigation. We find
the two enhanced regions average at 6.155 ± 0.681 μW m−2
sr−1
and
6.354 ± 0.616 μW m−2
sr−1
for E1 and E2, respectively, while the dim
region emits at a lower average of 3.212 ± 1.235 μW m−2
sr−1
, hence an
18%, up to 353% increase at both E1 and E2. This large range in emis-
sion enhancement is most likely from the high uncertainty in column
density, which affects the error propagation when calculating the
total emission. We, however, conclude that our division of emissions
of Uranus—whether the single Q(1,0−
) line or total H3
+
emission, into
distinctenhancementrelatedregions,isbothrobustandsignificant.
Comparing physical parameters between enhanced regions
provides an understanding of how they are enhanced. The average
temperature for the dataset is 585 ± 25 K, which aligns with previous
InthisArticle,wepresenthigh-resolutionIRemissionsatUranus
obtained over ~6 h in late 2006. We observe enhanced emissions that
appear close to latitudes of the UV northern aurora (delineated by
ref. 4). To confirm whether these emissions are auroral, the spectra
were analysed for temperature, column density and total emissions
to identify whether enhancements were thermally driven or created
byanionpopulationincrease.
UranusobservationsweretakenwiththeKeckIItelescopeonthe5
September2006,from07:26to13:24 UT,closetotheplanet’sequinox
in2007,usingtheNIRSPEC(Near-infraredSpectrograph)instrument27
withaKLatmosphericwindowfilter.A0.288 × 24 arcsecslitwasaligned
withtheplant’srotationalaxis(showninFig.1a).Spectraweregathered
between 3.5 μm and 4.1 μm where the fundamental Q-branch of H3
+
emissionslies(showninFig.1b;rawimageinExtendedDataFig.1).This
triatomichydrogenionisamajorconstituentofUranus’sionosphere
andplanetswhoseupperatmosphereisdominatedbymolecularand
ionichydrogen28
.Atotalof218spectraweretakenoveran~6 hperiod
withanintegrationtimeof~30 s.Thesewereco-addedinto13datasets
to enhance the signal-to-noise ratio (total integration time per set
was~27 min).Toincreasethesignal-to-noiseratiofurther,spatialpix-
els along the slit were grouped every 0.32 arcsecs (full details in the
Methods). The exact longitude of Uranus has been completely lost;
therefore, an arbitrary longitude has been selected for these results.
Astronomical seeing on the night averaged at 0.44 arcsec, which is
equivalenttoablurof14°latitudeand12°longitude.Duringtheobser-
vation,Uranusrotatedby~180°andhenceourfinalmappingspansan
areaupto~180°longitude.Unfortunately,alapseinguidingbetween
10:52 UT and 11:31 UT resulted in the loss of 2 longitudinal data bins,
leavingagapinthemiddleofourscans.Finally,resultspresentedhere
are not corrected for line of sight (LOS) (for example, see ref. 16) and
hence we expect infrared emissions to be enhanced near the planet’s
limb.AtJupiterandSaturn,auroralemissionsareLOSenhanced;how-
ever, Uranus’s solar extreme ultraviolet (EUV)-generated ionosphere
isdarkeratthelimbs7
,and,so,withoutadetailedunderstandingofthe
ionosphericbrighteningsource,itisnotpossibletocorrect.However,
asmuchoftheenhancedemissionsareawayfromthelimbs,weexpect
minimalchangeinthelocationofemissionspeaksaftercorrections.
To calculate the H3
+
intensities, temperatures, column densities
andtotalH3
+
emissionfortheupperatmosphereofUranus,thisstudy
focusesonfivequasi-thermalizedro-vibrationalemissionlinesofH3
+
,
Q(1,0−
),Q(2,0−
),Q(3,0−
),Q(3,1−
)andQ(3,2−
);thesephysicalparameters
werecalculatedfromafullspectrumbestfit,asdescribedinMethods.
0 50 100 150 200
Keck spectral pixels
0
10
20
30
40
50
60
Keck
spatial
pixels
Q(1, 0
–
) Q(2, 0
–
) Q(3, 0
–
) Q(3, 1
–
) Q(3, 2
–
)
0 0.2 0.4 0.6 0.8 1.0
Normalized intensity
a b
Fig.1|Observationalset-upandaveragedspectrumofUranusasobserved
byKeck-NIRSPEC.a,ThegeometryofUranusaswasobservedbyKECKIISCAM
(Slit-viewingcamera)andNIRSPECinSeptember2006.Theorientationofthe
spectrometerslitonthediskofUranusisshowninred,whichalignswiththe
planet’srotationalpoles.b,AnaveragedspectraobtainedbyKECKIINIRSPEC
between3.4 μmand4.0 μm,includingannotationsforQ(1,0−
),Q(2,0−
),Q(3,0−
),
Q(3,1−
)andQ(3,2−
)emissionlines,whichcanbefoundat3.9530 µm,3.9708 µm,
3.9860 µm,3.9865 µmand3.9946 µm,respectively.Panela madeinpartwith
UranusViewer3.1,Ring-MoonSystemsNode(https://pds-rings.seti.org/tools/
viewer3_ura.shtml).
3. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02096-5
temperatureobservations(ref.25for2006at608 ± 12 K).Theenhanced
regionshaveameantemperatureof585 ± 14 Kand564 ± 22 KforE1and
E2,respectively,withthedimregiontemperatureat593 ± 24 K,shown
in Fig. 2c. While the enhanced regions appear cooler, there is overlap
in temperature errors, so while we cannot conclude the emission is
anticorrelated with temperature, thermal processes cannot explain
theintensityenhancements.
Except at the planet’s limbs, EUV ionization produces a uniform
columnionizationrateacrossthewholedisk;however,enhancements
of column densities could be produced by enhanced particle precipi-
tation, suggestive of auroral activity. Shown in Fig. 2d, we observe an
averagecolumn-densitydifferenceof2.133 × 1015
m−2
attheenhanced
regions(4.017 ± 0.457 × 1015
m−2
and5.113 ± 0.826 × 1015
m−2
atE1andE2,
respectively)comparedwiththedimregion(2.432 ± 0.901 × 1015
m−2
).
These densities, on average, are higher (about two to five times
higher) than reported in ref. 25. Here a more through and complete
data-reductionprocesswasconductedoverthewholenightofobser-
vations rather than half the night, with densities presented in Table 1
Arbitrary longitude across Uranus (°)
90° N
60° N
30° N
30° S
60° S
90° S
0° 30° 60° 90° 120° 150° 180°
Arbitrary longitude across Uranus (°)
0° 30° 60° 90° 120° 150° 180°
Arbitrary longitude across Uranus (°)
0° 30° 60° 90° 120° 150° 180°
Arbitrary longitude across Uranus (°)
0° 30° 60° 90° 120° 150° 180°
0°
Latitude
across
Uranus
(ULS)
(°)
90° N
60° N
30° N
30° S
60° S
90° S
0°
Latitude
across
Uranus
(ULS)
(°)
90° N
60° N
30° N
30° S
60° S
90° S
0°
Latitude
across
Uranus
(ULS)
(°)
90° N
60° N
30° N
30° S
60° S
90° S
0°
Latitude
across
Uranus
(ULS)
(°)
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
Intensity
(µW
m
–2
sr
–1
)
±
0.05
µW
m
–2
sr
–1
Temperature
(K)
±
47
K
Total
emission
(µW
m
–2
sr
–1
)
±
5.33
µW
m
–2
sr
–1
Column
density
(×10
16
m
–2
)
±
0.20
×
10
16
m
–2
7
8
9
10
11
12
13
520
540
560
580
600
620
640
660
0.2
0.4
0.6
0.8
1.0
1.2
Enhanced Dim Intermediate
Sample size 23,677
a b
c d
Fig.2|Infraredintensity,totalemission,temperatureandcolumn-density
mappingsacrossUranusonthenightofobservations. a,MeasuredH3
+
Q(1,0−
)
intensitymappedacrosstheupperatmosphereofUranusagainstUranian
latitudeandarbitrarylongitude.b,TotalH3
+
emissioncalculatedfromthe
temperatureandcolumndensity(explainedindetailedinMethods).c,Estimated
temperaturesoftheH3
+
emissionsfromallfiveQ-branchlines.d,Estimated
columndensitiesofH3
+
emissionsfromallfiveQ-branchlines.Thelatitudeis
planetocentricwhereasthelongitudeisarbitraryduetothelossoftheULSsince
VoyagerII.ThesolidblacklinesmarkouttheboundariesofE1(left)andE2(right).
Withintheboundaries,theenhancedregionsareunshaded,thedimregionsare
shadedwithdotsandtheintermediateregionsareshadedwithdiagonallines.
Table 1 | Means and standard deviations of the Q(1,0−
) intensities, H3
+
ion temperatures, ion column densities and total
emission for the enhanced and dim regions
Mean Q(1,0−
) intensity (μWm−2
sr−1
) Mean temperature (K) Mean column density (×1015
m−2
) Total H3
+
emission (μWm−2
sr−1
)
Enhanced E1 0.723±0.010 585±14 4.017±0.457 6.155±0.887
Enhanced E2 0.716±0.009 564±22 5.113±0.826 6.354±0.616
Intermediate 0.650±0.032 572±19 4.134±0.761 5.354±0.664
Dim 0.472±0.086 593±24 2.432±0.901 3.212±1.235
4. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02096-5
aligning within the range of densities observed in previous investiga-
tions25,26
. In contrast to the temperatures, the enhanced region’s col-
umn density is on average 88% enhanced. Put simply, more emitters,
ratherthanhotteremitters,iswhatisresultinginmoreemission.
There are several scenarios that could lead to a column-density
enhancementatlocationsofincreasedH3
+
emissions.Onepossibility
isiftheionisproducedevenlyacrosstheplanetarydisk,thereissome
mechanism by which it is transported from the dim region into the
enhancedregions.
We do not consider meridional transport from the rotational
polestobesubstantialfortworeasons:first,Uranusisalarge,rapidly
rotating planet where it is difficult to overcome the Coriolis forces;
second,ifthereareequatorwardswinds,wewouldexpecttoseeaH3
+
bulgeevenlydistributedatlowerlatitudes.Thereisnothinginourdata
tosuggestpolewardsmeridionaltransport.
Zonal winds on Uranus are generally between 0 and 250 m s−1
.
A previous study29
found electron densities between ~109
m−3
(Voy-
ager egress) and ~1010
/1011
m−3
(Voyager ingress). Taking these figures
togetherwiththedissociativerecombinationcoefficientof~10−13
m3
s−1
(ref.30)suggestsamaximumhalflifetimeτ(H3
+
)oflessthan104
s,and
possibly as low as 100 s. Hence an individual H3
+
ion could be trans-
ported ~2,000 km. This is less than the ~30,000 km at the equator
to get from the centre of E2; although the distance from there to the
centreofE1isapproximatelyhalfthatvalue,itisstilltoofar.Hence,we
assumethattheH3
+
ions,theiremissionsandphysicalparametersare
representativeoflocallyproducedfeatures.
Anotherpotentialdriverforthedimregion’slowcolumndensities
could be ‘ring rain’ as seen at Saturn31
. Here, H3
+
destruction is modu-
latedbywatermoleculesintheplanet’sringstravellingalongthefield
lines into the planet’s lower latitudes. Figure 3a combines Fig. 2a and
theQ3 modelfromref.32,whichmapsUranus’smagneticfieldwithdip
angle contours, using contour steps of 20° dip angle (the angle made
withtheplanet’shorizontalplanebyitsmagnetic-fieldlines).Weexpect
theringraintoaffectonlyanarrowbandofdipangles(mappingtothe
planet’srings,1.6–2 RU),whereinFig.3aweobservethedimregionover
alargerangeofdipangles.Hence,quenchingringraincannotexplain
theemissionsweobserve.
Twomoremagnetic-fieldmodels(Q3
mp
andAH5;ref.4)havesincebeen
usedatUranus,replacingpreviousmodelswithamoregloballyrepresent-
ativemagnetopauseimagefieldandincludingUVauroralemissionsfrom
VoyagerII,respectively.Thesemodelsprovideastrongfittothesouthern
aurora,butthenorthernauroraispoorlyconstrainedasVoyagercrossed
magnetic-field lines that mapped close to the southern magnetic pole
twice,onceatadistanceof4.19RU,butonlyonceatthenorth,at>20RU.
Inaddition, the auroralmorphologymayhavechangedwithsolar-wind
pressureorbychangesinthepreferredauroralaccelerationregionabove
theplanet.Giventhiscomplexity,wefocussolelyontheQ3 model.
As none of the previous processes can explain the NIR enhance-
ment morphology, the most plausible explanation is that the density
enhancementsaredrivenbyauroralproduction.InpreviousH3
+
inves-
tigationsatJupiterandSaturn11–13,15,17,18
,wehaveobservedthestrongest
infrared emission enhancements and column densities at the auroral
regions, where particle precipitation results in significant ionization
intheupperatmosphere.Wefindthattheenhancedregionsstrongly
suggest auroral production and so consider that we have partially
mappedthenortherninfraredaurora.
Todeterminehowthe2006infraredemissionsalignedwithprevi-
ousmodels,wehavechosentonotaddalongitudeshiftintoourwork
due to the lack of known longitude (ULS) in 2006. Comparing Fig. 2a
andtheQ3 model(Fig.3a),weobserveintensitiesbetween60°and80°
dipangleatthesameangleaswheretheauroralovalsits,althoughthe
approximatelocationoftheauroralovalintheQ3 modelsitswithinthe
dimregion(similarinlocationtoFig.3b).Otherenhancedregionswith
pooralignment(wherethedipangledropsto20°)maybeduetomore
complex morphology within the surface magnetic-field structure, or
the effects of seeing (at least ~±12°) along with the low spatial resolu-
tion (~0.32 arcsec). We also note relatively weak emissions between
40° and 100° longitude. While most pixels in this region are ‘dim’, we
highlightthattheseemissionsremainbrighterthanthelimbs.Itmaybe
thatwhiletheenhancementisnotsignificantastheenhancedregion,
only the edges of the map represent the EUV ionized background H3
+
density.Thisweakercentralregioncouldbedrivenbyweakerauroral
precipitationandhencefurtherinvestigationsarerequired.
In Fig. 3b, we compare the infrared emissions against the L-shell
magnetic-field lines of the Q3 model. Here the emissions observed in
bothE1andE2extendoutpasttheoptimalL5shell,whichiswherethe
brightest UV emissions are observed by Voyager II and HST. Focusing
on E1, between 30° S and 60° S and before 30° ULS longitude, we find
noenhancedemissionsalignwiththeQ3 Lshells.Theseemissionsare,
however, located close to dayside O-source radio emissions33
, and
are close to n-smooth radio emissions observed in ref. 10, where the
authors suggested that these emissions arose from unusual particle
distribution from particle absorption by the Ɛ ring, which may act as
a driver for these infrared extended emissions. We do, however, find
a portion of E2 emissions fit within L shells of 3 and 5, where weak UV
emissionsinFig.3carelocated(~<100 R).
Figure 3c compares Fig. 2a with UV auroral emissions from Voy-
ager II in 1986. At Jupiter, UV and infrared aurora appear at similar
latitudes34,35
;however,attheauroraloval,ref.36foundUVandinfrared
auroralfeatures’brightnesscanvaryindependentlyofeachotherand
hence are not co-located. We should then not expect the brightest
NIR emissions to be co-located with the brightest UV emissions at
Uranus. Further differences between infrared and UV emissions can
also be explained by the ~15 min lifetime of H3
+
(at Jupiter) smoothing
out short-term (1–2 min) variability in UV emissions37
. A similar effect
mayalsooccuratUranus.
The enhanced H3
+
emissions are broadly spaced in latitude com-
paredwiththebrightestUVemission,wherethestrongestUVemissions
occurnorthofE1andonlyweakerUVemissionsappearclosetooratE2.
ThisspreadingofinfraredemissionssuggeststhatH3
+
emissionsoccur
more equatorwards (magnetic-field equator) than the UV emissions
and appear anticorrelated in terms of longitude. Differences in emis-
sion region may result from changes in the auroral drivers, changes
in the solar wind (as observed at Jupiter and Saturn38
); or short-term
variabilityassociatedwiththelocaltime.Thesemightbeviachanging
precipitationfluxorprecipitationenergy.Equally,contrastsinappar-
ent magnetic mapping of the two aurorae could originate from poor
alignment of our arbitrary longitude. It is difficult to draw too many
conclusionswithoutre-discoveringtherotationalphaseofUranus.
ThislikelydetectionofH3
+
auroraatUranushasbroaderimplica-
tions for Neptune, given the planet’s similarities (similar unaligned
and offset magnetic fields). Currently, we have not detected H3
+
at
Neptune39
, the cause suggested to be a cooler than expected upper
atmosphere28
.ThepresenceofinfraredauroraatUranussuggeststhe
potential for detecting aurora at Neptune, where past observations
mayhavebeentakenduringweakemissionperiods.
ConfirminginfraredauroraatUranusdirectlyassistsinexoplan-
etaryadvancementsaswarm-ice-giantworldsmakeupalargefraction
ofthecurrentpopulation40
.Auroraldetectionsfromexoplanetscould
provide upper atmospheric diagnostics. A detailed understanding
of Uranus could advance exoplanet knowledge, helping the wider
scientificcommunitytounderstandtheirionosphericcompositions.
Uranus also presents an ideal laboratory for observing conditions
during magnetic-field reversal, as the magnetospheric axis consist-
ently changes direction with respect to the solar wind, over a single
Uranian day41
. Current research requires analysis of volcanic rock at
Earth or modelling to identify the effects of a reversal42
. By undertak-
ing consistent observations, we can identify changes in atmospheric
processes,whichextrapolatedtoEarthcanenhanceourmodellingof
misalignedmagneticfields.
5. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02096-5
Methods
Introduction
This study uses 216 spectral images of H3
+
emission taken on the 5
September2006,theyearbeforeUranuswouldreachequinox.These
images were taken using the NIRSPEC instrument at the W.M. Keck
II Observatory using a KL atmospheric window filter that covers the
3.3–5.0 μm range, reduced through the spectrometer grating to a
3.35–4.0 μmrangetofocusonthefundamentalQ-branchemissionof
H3
+
(whichisknownfrompreviousinvestigations25,26
toemitwithasuit-
able signal-to-noise ratio). This wavelength range was used across all
imagesincludingthereferencestar(HR 215143)andflat-fieldimages.
Duetotheslitlengthof24″acrossUranus(whichatthetimesub-
tended 3.7″ in the sky), we positioned the disk of the planet at two
locationsalongtheslitwhentakingimages.Thefirstframe(knownas
theAframe)centredthediskofUranusinthetophalfoftheslit,while
the second frame (known as the B frame) centred the disk of Uranus
inthebottomhalfoftheslit.Bycarryingoutthispattern,forthesame
sky position we would have alternating observations of Uranus’s and
Earth’satmosphericemissionandthesecondwithjustEarth’satmos-
pheric emission. The latter data could then be subtracted from the
formertomitigatetheeffectofskyemissions.
Onceallimageswereobtained,thedatawerethenreducedusing
the Interactive Data Language (IDL)-based RedSpec data-reduction
pipeline, which shifts data into straightened two-dimensional arrays
byusingthereferencestarimages,asshowninthereferencematerial.
Tomitigatetheeffectofthermalcurrentsordeadpixelsonthedetector,
allreducedimageswerethencalibratedusingtheflatanddarkframes.
H3
+
intensitycalculationsandmapping
Takingtheimagesfromthereferencestarframes(whichatthetimewas
closesttoUranuswithinthenightskyandshowninSupplementaryFig.1),
thefluxcanbeestimatedbytakingaGaussianfitacrosstheblackbody
emission lines (similar to the Gaussian fit shown in Supplementary
Fig. 2a,b). Once found, the measured flux observed can be compared
againsttheknownintensityofHR 215143,whichisestimatedusingthe
work of ref. 43 with an α Lyrae (an A0) star. In this work, HR 215 143 is a
B7.5 V star, although the radius, mass and luminosity are of the same
or similar magnitude to that of A0 (A0V) stars44
; hence, we use the
calculations of ref. 43 as a close representation for the expected flux
of HR 215 143. The expected temperature of HR 215 143 is, however, at
approximately 11,000 K instead of 10,000 K (as expected of A0 stars)
as calculated from the work of ref. 45; this difference in temperature
isincludedinthecalculationsdescribedabove.
This ratio can then be used to convert detector counts from
images into a known intensity value, which was carried out across
all images. These images were then grouped into 54 sets of data and
aligned(incaseUranushadappearedtoshiftacrosstheslit)byusing
a Python script that detected the disk of the planet by measuring the
central position within the longest sequence of pixels with emission
values 1 s.d. greater than the background emission and shifting data
Latitude
across
Uranus
(ULS)
(°)
Latitude
across
Uranus
(ULS)
(°)
Latitude
across
Uranus
(ULS)
(°)
Latitude across Uranus (ULS) (°) Latitude across Uranus (ULS) (°)
Latitude across Uranus (ULS) (°)
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
a b
c
0° 30° 60° 90° 120° 150° 180° 0° 30° 60° 90° 120° 150° 180°
90° N
60° N
30° N
30° S
60° S
90° S
0°
90° N
60° N
30° N
30° S
60° S
90° S
0°
0° 30° 60° 90° 120° 150° 180°
90° N
60° N
30° N
30° S
60° S
90° S
0°
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
Intensity
(µW
m
–2
sr
–1
)
±
0.05
µW
m
–2
sr
–1
Intensity
(µW
m
–2
sr
–1
)
±
0.05
µW
m
–2
sr
–1
Intensity
(µW
m
–2
sr
–1
)
±
0.05
µW
m
–2
sr
–1
Fig.3|InfraredintensitymappingcomparedagainstpreviousUranus
magnetic-fieldmodelsandUVemissiondata. a,Q(1,0−
)mappedintensities
withtheQ3 model32
withcontoursrepresentingthecontoursof20°dipangles
tothethickcontinuouswhiteline,whichisthemagnetic-fieldequator.Here
theULShasbeensourcedandplacedintoourobservationsfromtheQ3 model.
Thegreybackgroundcolourrepresentstheareasthatwereunobservedinthese
observations.b,Q(1,0−
)intensities(whereonlytheenhancedregionhasbeen
highlighted)mappedalongsidetheLshellsof2(solidline),3(dashed),5(dotted),
10(dotanddashed)and20(solid)oftheQ3 model.c,Q(1,0−
)intensities(where
onlytheenhancedregionhasbeenhighlighted)mappedalongsidetheH2 band
emissionsintensitymapfromref.4.ToavoidobscuringtheUVemissions,the
darkgreybackgroundhasbeenremovedinthispanel.
6. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02096-5
by the required number of pixels so that individual spectra could be
co-added.
When all the data had been correctly lined up, to enhance the
signal-to-noise ratio, the data were binned into 13 temporal sets of
dataacross~6 hofobservations.Thiswascompletedbythesequence
in which A frames and B frames were taken, in an ABBA pattern where
two added A frames are subtracted by two B frames and averaged. By
averaging four datasets (over the previous 54 sets) at a time, it was
possible to obtain a spectrum with sufficient signal-to-noise ratio to
complete Gaussian fitting, as seen in Supplementary Data Fig. 2a,b.
Originally Uranus was found to cover just under 23 pixels (22.9 pix-
els) across the detector, the limbs of which were found by code that
searchedeachofthe13temporaldatasetsforenhancedemissionlines
that extended for 22–23 pixels; from this the approximate middle of
thediskcouldbededuced.
Afurtherenhancementofthesignal-to-noiseratiowasrequiredto
minimizetheerrorinintensityandsoa2 pixelweightedrollingaverage
was chosen to enhance the signal strength. This would mean starting
fromthenorthernlimb,thefirstandsecondpixelswereaveragedand
assigned to the first mapped pixel, then the second and third pixels
were averaged and assigned the second mapped pixel and so on. This
resultedinatotalof22 pixelsacrossUranus,allowingidentificationof
auroralorenhancedregions.
To find the observed intensity from all emission lines, the h3ppy
Python package (a Python version of the C++ fitting procedure as
detailed in ref. 35) was used. This produces multiple Gaussian fits
across a spectrum with a known range of wavelength, with intensities
foreachlinevaryingwithmodelledtemperatureandcolumndensity.
The calculations behind this are explained in detail in ref. 17. It should
be noted due to the changing LOS of the observer across Uranus’s
disk, the intensity will be enhanced at the limb of the planet due to
the observer effectively viewing through more of the atmosphere.
The background solar EUV when modelled at Uranus diminishes at
the edges and with the majority of the data localized away from the
limb,wehavenotadjustedforthiseffect.Theerrorsintheintensityof
Q(1,0−
)werecalculatedbytheerrorsinfittingaGaussiancurvewiththe
observedemissionline(errorspredominatelyarisingfromtheheight
andwidthofthefit).
H3
+
ro-vibrationaltemperaturecalculations
ByapplyingafullspectrabestfitacrossemissionlinesQ(1,0−
),Q(2,0−
),
Q(3,0−
), Q(3,1−
) and Q(3,2−
), the ro-vibrational temperatures can be
calculatedusingabinitioEinsteinAcoefficients—physicalparameters
ofH3
+
spectraemissionlinesasdetailedbyref.46andtheupperenergy
levelsasdescribedbyref.47.Thisprocessiscarriedoutwiththeh3ppy
package (see Supplementary Fig. 3 for a visual representation of this
fitting with an averaged spectrum from the 5 September) assuming a
quasi-localthermodynamicequilibriumH3
+
spectrafit20
.
H3
+
column-densitycalculations
This data product was calculated by dividing the measured intensity
fromtheobservedemissionlinesbythetheoreticalemissionpermol-
eculeforalltheQ-branchemissionlinesmentionedinthetemperature
calculations,asdescribedbyref.24.ItshouldbenotedduetotheLOSof
theobserveracrossUranus’sdisk,thecolumndensitywillbeenhanced
atthelimboftheplanetduetotheobservereffectivelyviewingthrough
theatmospheretwice.Atpresent,theseresultshavenotbeenadjusted
for this effect, as most of the data are localized away from the limb of
theplanet,butweestimatethat,withintheauroralregionsdiscussed,
thisenhancementwouldbe14%.
H3
+
totalemissioncalculations
Usingthecalculationsofref.46,thetotalemissioncanbecalculatedby
theproductofthenumberofionsbythetemperature-dependenttotal
emissionpermolecule(Emol
)whileassuminglocalthermalequilibrium.
Thisrequiresboththecolumndensityandtemperatureovertwoormore
emissionlines),wheretemperatureisusedtocalculateEmol
.Itshouldbe
highlightedthatduetotemperaturesstayingbetween500K≤T≥900K,
suitablecoefficientvalueswereselectedtocalculateEmol
.
Dataavailability
The NIRSPEC raw data used in this study (and subsequent raw data
used in Figs. 1b, 2 and 3) are publicly available on the Keck Observa-
tory Archive (KOA) at https://koa.ipac.caltech.edu/cgi-bin/KOA/
nph-KOAlogin and included with the source data. Reduced and cali-
bratedimagesusedinthiscurrentstudycanbeobtainedthroughthe
RedSpeccode(discussedbelow)withthefinaldatausedinthefigures
of this paper available with the source data and https://github.com/
physicist-et/Uranus_AuroraKeck_0905.Sourcedataareprovidedwith
thispaper.
Codeavailability
RedSpec is a data-reduction package in IDL, designed to reduce and
process spectral images from NIRSPEC and is available at https://
www2.keck.hawaii.edu/inst/nirspec/redspec.h3ppyisaH3
+
emission
modelling and fitting package in Python and is available at https://
github.com/henrikmelin/h3ppy. All remaining code used to extract
thereduceddata,alignitforusewithh3ppyandGaussianfitfunction
andmappingvariablesareavailableathttps://github.com/physicist-et/
Uranus_AuroraKeck_0905.
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Acknowledgements
The UK STFC studentships ST/T506242/1 and ST/N504117/1 supported
the work of E.M.T. and M.N.C., respectively. The STFC James Webb
Fellowship (ST/W001527/1) at the University of Leicester, UK supported
H.M., and the UK STFC Consolidated Grant ST/N000749/1 supported
T.S.S. The data presented herein were obtained at the W. M. Keck
Observatory, which is operated as a scientific partnership among the
California Institute of Technology, the University of California and
the National Aeronautics and Space Administration. The observatory
was made possible by the generous financial support of the W. M.
Keck Foundation. The authors are indebted to Mark Showalter for
their assistance with Fig. 1 of this article. The authors recognize and
acknowledge the very significant cultural role and reverence that the
summit of Maunakea has always had within the Indigenous Hawaiian
community. We are most fortunate to have the opportunity to conduct
observations from this mountain.
Authorcontributions
E.M.T. performed data reduction and data analysis, and contributed
to the writing and editing of the paper. H.M. was responsible for
the data analysis with the use of h3ppy. T.S.S. contributed via
data reduction and data analysis. M.N.C. was responsible for IDL
to Python code conversion for two-dimensional mapping over
a three-dimensional surface. K.K. and R.W. contributed to the
discussion and editing of the paper. S.M. is the principal investigator
for the observations of Uranus taken in 2006 and contributed to the
paper via discussion and editing of the paper.
Competinginterests
The authors declare no competing interests.
Additionalinformation
Extended data is available for this paper at
https://doi.org/10.1038/s41550-023-02096-5.