ppt

1. MILKY WAY
In the universe, matter is not homogeneously distributed, but on the contrary,
it’s concentrated in certain areas forming GALAXIES, which form large groups called
GALAXY CLUSTERS. Among these areas there are huge VOIDS OR EMPTY
SPACES.
THE UNIVERSE
EMPTY SPACE GALAXIES
GALAXY CLUSTER

2. A galaxy is a large group of stars, between 100 000 and
500 millions. Towards the center of the Galaxy, the stars
are close together. An enormous cloud of gas and dust,
called nebula, surrounds the stars
Portion of the Carina Nebula
The Rosette Nebula
STARS are made up mainly of hydrogen and helium, the two
most abundant gases in the Universe. Inside them there are
nuclear reactions which produce huge amounts of energy.
They are so hot inside that they emit heat and light.
GALAXIES
Within a galaxy we can find groups of
stars relatively close to each other. They
are open clusters.
STARS

3. STRUCTURE OF GALAXIES
Inside galaxies we can find the following structures:
STAR CLUSTERS:
They are
groupings of
stars held together
by gravity
NEBULAE: They consist of clouds of
gas (mainly H and He) and interstellar
dust. These are the places where stars
are born, also they can be the remains
of a star that died. Ex.: Pillars of
Creation in the Eagle Nebula, 7000
light years away
MULTIPLE STELLAR SYSTEMS: They are two or
more stars held together by gravity that revolve
around a common center. They are often apparently
seen as a single star. They are commonly double or
binary systems. Ex.: Alpha Centauri, the nearest star
to our Sun is a binary system.
BILLIONS OF
STARS

4. Many stars have planets that revolve around them forming planetary systems, like
our Solar System
PLANETS are bodies which orbit some
stars. They do not emit light; they receive
light from the star and reflects it (that’s why
we can see them).
Some planets have SATELLITES
or moons, They are small bodies
that orbit a planet. The Earth’s
natural satellite is the Moon
PLANETAY
SYSTEMS:
They consist of a
central star which
have other bodies
orbiting around it

5. 1) ELLIPTICAL GALAXIES: These
galaxies have little to no structure They
are rich in old stars and have little
gas and dust. They are the most
common type of galaxy. It is believed
that large ones come from collision and
merging of other galaxies.
3) SPIRAL GALAXIES:
These galaxies are disk-
shaped either a round
central hub (unbarred) or a
hub shaped like a bar
(barred). Gas clouds and
young stars are
arranged in the spiral
arms and old stars form
the halo surrounding the
central disk.
4) BARRED SPIRAL GALAXIES: In the
central disk there is an axis or
longitudinal bar
2) IRREGULAR GALAXIES:
They look chaotic. They have
no nucleus. They are
considered to be the result of
collision of galaxies. So, they
contains a mixture of
interstellar gas and dust,
old stars and young stars
TYPES OF GALAXIES

6. Our galaxy is an spiral shaped galaxy called the Milky Way. The Milky Way belongs
to a galaxy cluster called the Local Group. The Local group is made up of about 33
galaxies. The closest galaxy to us is Andromeda

7. STARS (the
Sun), gas and
dust clouds,
dark matter and
dark energy
GALAXIES
(Milky Way)
GALAXY
CLUSTERS
(Local Group
and Virgo)
SUPERCLUSTERS
(Local supercluster)
GALAXIES, GALAXY CLUSTERS AND SUPERCLUSTERS
Galaxies are made up of billions of stars, gas and dust clouds and dark
matter, gravitationally bound. There are over one hundred billion (1011) galaxies
in the observable universe. They are flattened ellipsoid shape, with a thicker area
in the core. Our galaxy, the Milky Way, is about 10,000 light years in diameter. The
nearest star to our Sun is Alpha-Centauri.
Galaxies move in the space and usually are grouped to form
the so-called galaxy clusters, which, in turn, may form larger
aggregates called SUPERCLUSTERS that may contain
thousands of galaxies. For example, the Milky Way is part of
the Local Group (a galaxy cluster comprising 30 galaxies, of
which Andromeda is the nearest galaxy to us). The Local
Group, in turn, orbits around the large cluster of galaxies
called Virgo. The Virgo cluster, along with the Local Group
and other clusters form the LOCAL SUPERCLUSTER. All
these clusters are moving in the same direction, although the
reason is not yet known.

8. THE MILKY WAY TRANSIT MAP

9. MILKY WAY GALAXY NEIGHBOUR

11. WHERE DO WE LIVE IN THE UNIVERSE?

12. GALACTIC FILAMENTS Observations of galaxies show that on large
scales, they are not randomly distributed in
the Universe. Most are found in groups and
clusters which are themselves part of large-
scale structures such as sheets and
filaments. These structures contain millions of
galaxies and are separated by large voids in
which very few galaxies are found.
With lengths of hundreds
of millions of light
years (but thicknesses of
only ~20 million light
years), galactic
filaments are some of the
largest known structures
in the Universe, and are
partially responsible for
the ‘honey-comb’
appearance evident in the
image
Each individual do represents a
single galaxy, and long filaments
made up of thousands of
galaxies are clearly visible. The
bright regions at the intersections
of filaments are POTENTIAL
GALAXY SUPERCLUSTERS.

13. GALACTIVC FILAMENTS, LARGE-SCALE STRUCTURES IN THE UNIVERSE

14. 1) ORDINARY MATTER or baryonic matter (4%) Which
can be:
- VISIBLE (stars, planets, intergalactic hot gas) (0.4%)
- INVISIBLE (black holes, intergalactic gas) (3.6%)
2) DARK MATTER (21%)
3) DARK ENERGY (75%)
ORDINARY MATTER DARK MATTER DARK ENERGY
It’s made up of ATOMS, the
chemical elements of the periodic
table consisting of protons,
neutrons and electrons. Around
70 -75% of this matter is
hydrogen (the simplest element),
about 25% is helium, and there
are small amounts of the other
108 elements of the periodic
table.
It emits or reflects light, so that
we can detect radiation coming
from it (with exceptions).
It has gravitational effects
Its composition is
unknown. It’s assumed that
dark matter is composed of a
type of particle that has not
been found in a laboratory
yet.
It does not emit or reflect
light, so we do not receive
any radiation from it.
Its existence is inferred from
their gravitational effects on
rotational speed of galaxies
and inside the galaxy
clusters, and also from
mathematical predictions of
the total mass of the universe
It’s nature is unknown.
It is homogeneously
distributed throughout
the universe and has
opposite effects to
gravity, so it’s thought to
be probably causing the
universal expansion to
accelerate
UNIVERSE COMPOSITION

15. Dark matter was proposed by astrophysicists, due to discrepancies between the mass of large
astronomical objects determined from their gravitational effects and the mass calculated from
the "luminous matter" they contain: stars, gas and dust.
HOW DO WE KNOW THAT THERE MUST BE DARK MATTER IN THE UNIVERSE ?
Stars in galaxies rotate too fast according to the
visible mass enclosed in its orbit. They should be
thrown out unless galaxies had more mass (dark
matter) that attracted them.
Calculated mass from visible
matter is not enough to hold
together the galaxies that form the
cluster. They should move away
unless there were more mass (dark
matter) in the cluster to keep them
together

16. METHODS TO STUDY THE UNIVERSE
1) Analysis of the matter that
comes from outer space
(meteorites, comets remnants,
etc..)
2) Analysis of the radiation
that comes to us: light and
radiation (radio waves,
infrared radiation, etc..)
detected by telescopes and
radiotelescopes both
terrestrial and space ones.
3) Analysis of the images
and data obtained by
satellites and space
probes (devices that are
sent into space to do
research work and do not
return)
Hubble Telescope Cassini Probe

17. LOOKING BACK
Light travels at an enormous but finite speed, (300,000 km/s), therefore when we see, for
example sunlight, that light has taken a long time to come (8 min. 18 sec.), So we are
actually seeing what the sun was like 8 minutes ago. Thus, when we see a star which is
4 light years away, it means that the light from it has taken four years to reach us. So, looking
at that star, what we're seeing (what reaches our eyes), is not what currently occurs there,
but what happened in that star four years ago. We are seeing the past!
Considering this, if we observe a star that is a million
light years away, we are seeing what the universe was
like a million years ago! Hence the interest of
astronomers on looking so far. This technique is
completely necessary, especially to look into the
origin of the universe and what its first steps were
What about the record? Hubble space telescope can
see what happened 13,200 million years ago! And COBE
and WMAP probes almost the origin of the Universe.
THE
FURTHER
WE CAN
SEE, THE
MORE TO
THE PAST
ARE WE
LOOKING AT

18. WHAT IS LIGHT?
• Light is a form of radiated energy which travels as elementary PARTICLES called
photons. These photons travel through the universe at a speed of 300,000 km/s. The
mass of a photon is zero, and they can travel even through empty space.
• Light is transmitted as a WAVE also. A wave is a form of energy transmission from one
point to another in space, which doesn’t involve displacement of matter. The series of
“peaks and valleys” or “ups and downs” are called wave.
• Thus, LIGHT HAS A DUAL BEHAVIOUR: like a wave and a particle
• Waves are defined by their FREQUENCY (photon number of oscillations per second),
which is proportional to its energy: the higher frequency, the higher energy; and by its
WAVELENGTH (distance between crests), which is inversely proportional to its energy: the
longer wavelength, the lower energy
• .
• Not all photons/waves contain the same amount of energy. According to the energy
containing at photons/waves, is defined the electromagnetic radiation spectrum:

19. ELECTROMAGNETIC RADIATION SPECTRUM

21. Violet 380-450 nm
Blue 450-495 nm
Green 495-570 nm
Yellow 570-590 nm
Orange 590-620 nm
Red 620-750 nm
THE HUMAN EYE
The human eye is only capable of capturing
photons whose wavelength ranges from 750 nm
(red) to 380 nm (violet). In this range of
values ​​are, in descending order, the
wavelengths corresponding to the Rainbow
colours. That’s what we call visible light:
However, current telescopes, radio telescopes
and other devices are capable of detecting
radiation of any wavelength. Thus, analysing
the light/radiation that comes from any point
in space we know their composition,
distance, movement and even its history. For
example, the beginning of the universe in a big
explosion (Big Bang).

22. Doppler effect is the apparent change in the
frequency of a wave produced by the relative
motion of the source with reference to the
observer.
In the case of sound waves the pitch of a sound
emitted by a source approaching the observer is
higher than if the source moves away. The same
phenomenon occurs in the case of
electromagnetic waves.
In the case of the visible spectrum of
electromagnetic radiation:
- If the object moves away, its light is shifted to
longer wavelengths, moving towards red.
- If the object is approaching, the light has a
shorter wavelength, moving toward blue.
As it approaches, the sound waves are compressed
and you hear a higher sound (A). Moving away, the
sound waves are stretched and you hear a lower
sound (B).
The light coming from distant stars and galaxies is REDSHIFTED (stretched waves) when
they move away from us and it SHIFTED TO BLUE-VIOLET (compressed waves) when
they approach us.
DOPPLER EFFECT, THE EXPANDING UNIVERSE AND THE BIG BANG

23. THE EXPANDING UNIVERSE AND THE BIG BANG
Studying the light coming from galaxies it was found out that light from
distant galaxies is shifted toward red due to the Doppler effect. This
means that most galaxies are moving away from the Milky Way. The
exception were the closest galaxies (which are part of our Local Group) as
Andromeda, whose light comes blueshifted.
Galaxies are moving away from each other, but those that move away
faster show their light more redshifted. Hubble noticed that the recession
speed of galaxies was greater the farther they were (Hubble’s Law).
The farther the galaxies are, the faster they move away, and no one
approaches another one. How is it possible?
Edwin Powell Hubble related the moving away of galaxies with an Expanding Universe: The Universe
increases in size (volume) in time because the space between galaxies increases. The universal
expansion is the only way we can explain that all galaxies move away from each other, without approaching
anyone.

24. Universal expansion is an expansion of space, while galaxies (its
own motions outside) maintain size and position.
A good model to understand it is to represent the universe with one
dimension less , like the surface of a balloon. In it, galaxies would be
paper stickers pasted on the surface. As the balloon is inflated, galaxies
move away from each other and observers of each galaxy have the
impression that all others galaxies move away from them. It is the
space between galaxies which increases while they remain more or
less stationary. Thus, galaxies lack of their own velocity rate
Explaining the redshift of the light coming from distant galaxies based
on the Doppler effect is, therefore, inaccurate. However, redshift takes
place and we use it to determine the distance at which objects are, but
it does not occur due to Doppler effect, it’s due to expansion of the
universe that "stretches" the photons, displacing its wavelength to
red one.
If we see redshift in the light
coming from distant galaxies it is
because that light has been
travelling through expanding
space long , and photons have
been "stretched" with it. It can help
us to see this image.

25. THE ORIGIN OF THE UNIVERSE: THE BIG BANG
The universe is expanding: That implies that if you go back in time, galaxies were getting
closer and the Universe was smaller and smaller. Finally, the conclusion is that the Universe
originated from a single point, a primeval atom, by a gigantic explosion called the Big Bang
This Big Bang happened about 15,000 million years ago.
Before the Big Bang, according to
scientists, the vastness of the
observable universe, including all
its matter and radiation, was
compressed into a hot, dense mass
just a few millimeters away. This
almost incomprehensible state has
been speculated that existed just a
fraction of the first second of time.
Massive blast allowed all known
matter and energy of the universe,
including space and time, to arise
from some type of unknown energy.

26. 3. The microwave background
radiation. It’s detected a relic radiation in
all directions that represents the "glow" or
“switch on" of the initial explosion that
comes to us today as microwave due to
the expansion of the Universe. Later we
will see its source.
EVIDENCE CONFIRMING THE BIG BANG THEORY
2. The atomic composition of the
Universe (75% H, 25% He) which, as we
shall see, is consistent with this theory.
1. The Universal expansion itself.
Currently, from the data provided by
COBE spacecraft (Cosmic Background
Explorer) and WMAP (Wilkinson
Microwave Anisotropy Probe),
perturbations of this background
radiation have been studied and
analyzed, and the results confirmed that
the Big Bang occurred 13,700 m and the
early universe was extremely hot, from
about 1013 - 1031 K and very very dense.
They Also revealed that big bang radiation
contained fluctuations from the beginning,
which are the reason why matter is no uniformly
distributed, but it is concentrated in some areas,
leaving a lot of empty space.

27. The theory holds that, in an instant (one trillionth of a second) after the Big Bang, the
universe expanded at an incomprehensible speed from its origin: the size of a pebble to
reach an astronomical size (inflation phase).
Apparently, its expansion continued later but much more slowly, over the next few
billion years. Although nowadays we know it is accelerating due to dark energy.
UNIVERSE EVOLUTION
As the universe expands
over time, the size
(volume) increases, but
temperature decreases
and its density too.
Thus, as time passed the
material were getting
cooler and began to
form diverse types of
atoms, and these
eventually condensed
into stars and galaxies
of our present universe.

28. ELEMENTARY
PARTICLES
(electrons, positrons,
neutrinos quarks and
photons)
HOMOGENEUS
COSMIC SOUP
Protons,
neutrons,
electrons,
positrons,
neutrinos and
photons
(“caught” by
particles)
PRIMARY
NUCLEOSYNTHESIS
(75% nuclei of H and
25% nuclei of He)
FIRST
LIGHT
ATOMS
FORMATION
(75% H y
25% He)
STAGES IN THE UNIVERSE EVOLUTION
A) OPAQUE OR DARK AGE OF THE UNIVERSE (Up to 300,000 years after the Big Bang)
1. Inflation phase
2. Stages of matter formation:
- As temperature drops, elementary particles begin to interact with each other to form stably particles of
increasing size as protons and neutrons.
- About 3 minutes after the Big Bang temperature had dropped enough and protons and neutrons joined
and gave rise to the first light nuclei. This process is called primary nuceosynthesis, and lasted only a
few minutes. Nuclei formed almost the current composition of the Universe: 75% hydrogen and 25% helium.
(In form of “plasma”, in which nuclei and electrons are separated from each other)
- From atomic nuclei, when the temperature dropped below 3000 K (300,000 years after the Big Bang) atoms
formed the first chemical elements: 75% H and 25% He
- One hundredth of a second after the Big Bang the universe began to cool (1013 K)
due to expansion and the first elementary particles of matter appeared : electrons,
positrons, neutrinos, quarks and photons. Matter and radiation (photons) interact
and are coupled to form a hot, gaseous phase called homogeneous cosmic
soup or elementary particles soup. Temperature was so high that particle
interactions were very unstable.

29. B) LIGHTINING ON THE UNIVERSE and TRANSPARENT UNIVERSE (300,000 years after BB)
- 300,000 years after the Big Bang, temperature
dropped below 3000 K and atomic nuclei and
electrons joined to form electrically neutral ATOMS: H
(75%), and He (25%). As a result, photons broke away
from matter and breakup, disengagement or
decoupling of matter and radiation took place.
- This initial radiation of light travelling through space is
what today is recorded as microwave background
radiation. That initial glow of light has become
microwave because the expansion of the universe has
"stretched" their wavelength.
- Data obtained by COBE probe when the Universe
was only 300,000 years old indicate that this glow was
not completely uniform but had regions of higher
density material. These denser regions, in which the
gravity was increased, attracted the matter to itself,
and while it was added, matter was fusing together in
small units. That’s how it began to form dense
objects: So first stars were made, and by meeting
these, first galaxies (approx. 5,000 m y ago). Later
first supernovae appeared and heavier atoms began
to appear.
- Photons, now free from interactions with particles,
began to travel freely through space: light began to
travel through space and Universe became
transparent to light.

30. STAGES OF UNIVERSE EVOLUTION

32. THE HISTORY OF THE UNIVERSE

33. Arno Penzias and Robert Wilson with
6-m antenna to detect microwave in the
Milky Way
"THE ECHO OF THE BIG BANG"
COSMIC BACKGROUND RADIATION
In 1965 two young astronomers, Arno Penzias and Robert Wilson, built a
strange 6m antenna to catch possible microwave from the Milky Way. They
didn’t find it, however, they detected a mysterious radiation observable in
all directions of the sky that remained omnipresent day and night all the
year long. First, they thought it might be "noise" caused by the abundant
droppings left by the pigeons on their big antenna. But, in spite of a careful
cleaning of the antenna, the situation didn’t change . It was a highly uniform
sign that seemed not to come from our galaxy. They mentioned the strange
discovery to some colleagues who quickly identified the radiation as the
one predicted by the proponents of the theory of the Big Bang two
decades earlier. Thus, the discovery became to be an evidence of the big
bang as the origin of the Universe.
We can capture this
radiation in our homes
with old analogy TVs:
When any channel isn’t
tuned, 1% of the "snow"
that can be seen on the
screen is that background
radiation captured by the
antenna device ....
"Picture" of the cosmic
microwave background by the
WMAP probe obtained in 2003.
This radiation was generated
when the atoms began to form
about 300,000 years after the
Big Bang. In the picture, the
different colours represent
density differences in the
Early Universe, which led to
the formation of galaxies

34. THE FUTURE OF THE UNIVERSE

35. THE FUTURE OF THE UNIVERSE
Nowadays we know that when the universe was between 5,000 –
6,000 m.y. old and was half the size it is today, dark energy
already existed. By that time the rate of expansion of the universe
began to accelerate. Other data that reinforce this accelerated
expansion is that when the universe was about 1,000 m.y. old,
mergers between galaxies were very common, and this
process has been decreasing increasingly, until about 6,000 m.y.
after the Big Bang, when these mergers were almost nonexistent,
as at present time. Also at this time stars formation decreased
too. We know that most stars we can see now were born in the
first half of the life of our universe.
Before the existence of dark energy was discovered, astronomers had proposed two possible futures for the
Universe. Following this discovery a third theory appeared :
1) If the Universe density were greater than a critical value, there would come a time when mutual gravity
would exceed the expansion. The Universe would reach a maximum size and then begin to collapse. It
would be getting smaller, denser and hotter until becoming in a similar state to its beginning. The process is
called the “Big Crunch”, and we would be talking about a cyclic universe.
2) If the Universe density were equal or less than the critical value, the expansion would never stop. Star
formation would cease and the Universe would become less dense and cooler. When the temperature
reached almost absolute zero, we would be talking about the “thermal death of the Universe”.
3) Predominance of dark energy would move galaxies away from each other at an accelerated pace and
they`d end up as islands in a vast emptiness. Dark energy would end up separating all objects joined by
gravity: It would disintegrate galaxy clusters and galaxies, planets would separate from their stars, they would
be disintegrated, and even atoms would be destroyed. It Is the theory of the “Big Rip”.

36. A strong radiation emitted from cores of many galaxies was found, that
would mean that there probably exists a black hole inside them.
BLACK HOLES
Black holes are high density material concentrations. As a result, its
gravitational field is so huge that not even light with its extraordinary
speed can escape from it. So, we can’t see it, and we say it’s “black”
Almost all galaxies that have been deeply studied
contain a black hole in its center . The one
occupying the center of the Milky Way is called
Sagittarius A *. Its mass is 3 million suns and its
current event horizon is 7.7 million km away
It has such a gravity power that it absorbs anything that is too close to it.
How close? For each black hole there is a no return distance or “event
horizon” so that anything that will trespass it will be absorbed hopelessly.
But fortunately, gravitational attraction decreases very rapidly with distance,
so that, out of this safety limit gravitational pull is zero and bodies are not
attracted to it. The paradox is that the more bodies fall on it, the greater
its mass is and therefore its gravitational attraction increase and its
event horizon is extended.
Black hole devouring a star

37. So, if it do not emit light, How do we know about their existence?
- We know about it from radiation (especially X-rays) released by accelerating matter just before falling into
the large gravity well.
- Also because sometimes we see stars rotating around an "empty" to which depends gravitationally. There
must be a black hole.
Black holes are formed when a very very massive star runs out of fuel
and dies, with a big explosion called supernova. The remaining residue can
be a black hole.

38. Theories about
black holes
BLACK HOLES INTO GENERAL RELATIVITY
We could imagine space as a sheet gripped by the extreme to remain stretched. If
we throw a bowling ball on top, it will bend. Something similar, according to the
theory of general relativity, makes a star into space, The greater the mass of the
ball, or star, is, the steeper the curve generated is. In a black hole curvature acquires
such an intensity that space is "broken“, it’s made a "hole". This hole, more properly
called singularity, is a real challenge, the laws of physics as we know them today,
including general relativity, lack there of validity.
Photons that a distant observer could see increase in
wavelength and "redden" to "fall" into the black hole

39. STARS
Stars are spherical bodies that generate energy as a result of special
reactions that take place inside them: They are high temperature nuclear
fusion reactions or thermonuclear reactions. This energy is released into
space as all types of electromagnetic radiation (Light, heat, x-rays, gamma-
rays, UV-rays, etc.) neutrinos and solar wind (jets of tiny electrically charged
subatomic particles)
In the universe there are stars of very different ages and stages of development. It is calculated first stars were formed about
13,200 m.y. ago, shortly after the beginning of the universe. Large number of stars were formed about 5,000 m.y. ago.
Stars form (are born), evolve in a series of stages from youth, maturity and old age, and eventually die
off after a time more or less long. The larger a star (more massive) is, the faster its evolution and the shorter
its life is.
STAR BIRTH
Stars are formed in dense regions of a nebulae, when the dust and gas that
it contains is compressed (pushed by the shock wave from the explosion of a
nearby supernova or the collision of galaxies), and its density increases. When
the nebula contracts, gas and dust begins to spin and focus on the center
(process of gravitational collapse). This increasingly density raises the
temperature progressively and forms a very hot core called protostar.
Around it, in the equatorial plane of the core, remains a flat disc with the
leftover material, from which planets will be formed (protoplanetary disc)
When temperature reaches millions of Kelvin degrees, nuclear fusion
reactions start and therefore the core begins to emit radiation and a star
is born.

40. STAR AND PLANETARY SYSTEM FORMATION

41. Energy emitted by stars comes from thermonuclear fusion reactions
that take place in the core, where a temperature of about 107 ºC is
reached. In these reactions light nuclei merge to form new nuclei of
heavier atoms. At first, main reaction is fusing two hydrogen nuclei
to form a helium nucleus. This process releases large amounts of
energy in form of all types of radiation (light, heat, X-rays, Gamma-rays,
UV-rays. etc.) and stellar wind (particles and ionized gas)
- In a 1st phase the hydrogen is transformed successively in
increasingly heavier elements of the periodic table, up to
iron: H > He > C > O > Ne > Mg > Si > Fe.
Stars do this at various stages of their life. The biggest
stars move more in the series of chemical elements formed
than medium or smaller stars that fail to complete the series.
- A 2nd phase, takes place only at the end of giant stars
life, when they explode in supernovas and temperature
rises further to form the heavier than iron atoms of the
periodic table.
STARS AND CHEMICAL ELEMENTS FORMATION
STARS ARE THE FACTORIES WHERE ALL CHEMICAL
ELEMENTS OF THE PERIODIC TABLE ARE MADE
STARTING FROM HIDROGEN
It starts with the lightest atom of all, the hydrogen, to form
increasingly heavy atoms, at different stages of the life of a
star:

42. 1) MAIN STAGE: YOUTH AND MATURITY OF THE STAR
- At the beginning of its life stars are BRIGHT BLUE STAR and their main
component is hydrogen, which by nuclear fusion reactions is transformed
into helium nuclei. These heavier than hydrogen nuclei , are placed at the
center of the star.
- Over time, its temperature and luminosity increases, and becomes a
YELLOW STAR (like our Sun currently), but basically the same reaction takes
place.
STAGES OF A STAR LIFE
2) OLD AGE AND DEATH
From the helium formed, stars formed now, by nuclear reactions, carbon,
which is placed again in the center of the star. When enough carbon is formed,
it’s originated successively, by the same process, oxygen, neon, magnesium,
silicon and iron. The result is a RED GIANT STAR with an onion layered
structure, with heavier chemical elements in the center and progressively more
light toward the surface. The star evolves increasing heavy elements content
and decreasing hydrogen
From this point, the evolution of a star is different depending on its size:
Small and medium stars (M <9 MSun): When fuel is exhausted (He) the star dies
expelling outer layers as a planetary nebula, while the core (rich in C and O) shrinks
forming a WHITE DWARF. This one will cool slowly to burn out in a BLACK DWARF.
The cooling time is so long that there is still none.

43. PHASE OF HEAVY ELEMENTS
FORMING IN A SUPERNOVA
(EXPLOSION)
Stellar
Evolution
Giant stars (Red supergiants) (m> 9 Msun): When fuel runs out, they suffer an intense gravitational
collapse: The nuclear stove stops and gravity acts to fall toward the center trillion tons. An instant nuclear
fusion produces chemical elements heavier than iron (gold, silver, uranium, etc.). The energy released
causes a big explosion of the star named SUPERNOVA.
- Outer layers, with the chemical elements formed, are ejected forming a remaining nebula (from which stars of
2nd or 3rd generation may form again).
- The core forms a heavy residue which can be a NEUTRON STAR (very dense) or in cases of supermassive
stars (M> 30 Msun) one BLACK HOLE may be formed.
Our Sun is an average star, nowadays a yellow star that was formed about 4,600 m.y. ago. It is in the middle
of its life, so it still has many millions of years ahead. But when it passes to the phase of Red Giant it will
expand greatly and will occupy the orbits of Mercury, Venus and probably the Earth. Then, it will expel its outer
layers into a planetary nebula and the core will remain as a white dwarf, which slowly will turn into a black
dwarf.

45. The Solar System comprises the Sun and a large
number of bodies attached to it by gravity:
8 Planets, their moons, 3 dwarf planets (Ceres in
the asteroid belt and Pluto and Eris, on the Kuiper
belt) comets, asteroids and meteorites
SOLAR SYSTEM
It was formed about 4,600 m.y. ago, from gas and
cosmic dust of a nebula located in one of the spiral
arms (Orion arm) of the Milky Way. When the
nebula became a rotating disk originated, in the
center, the star, and from the rest of the disc material
all planetary bodies in the system.
Planets revolve around the Sun describing
elliptical orbits (the Sun located at one focus), all
located in the same plane, called plane of the
ecliptic. The direction of translation is
counterclockwise. The axis of rotation of planets
is almost perpendicular to the ecliptic, except
Uranus, which is almost parallel to it. They all rotate
counterclockwise, except Venus, which makes it
clockwise.
Pluto stopped being a planet in 2006. Its orbit crosses
the Kuiper belt asteroid (beyond Neptune)
Dwarf planets orbit around the Sun, but its gravity
is insufficient to clear its orbit of neighboring bodies.
Its orbit is located or through any of the two belts of
asteroids (main belt and Kuiper)

46. SMALL ROCKY PLANETS AND GAS GIANT PLANETS
INNER, TERRESTRIAL OR ROCKY PLANETS:
They are Mercury, Venus, Earth and Mars.
• They occupy the inner orbits of the solar
system (within the main asteroid belt)
• They are small compared to the rest
• Their surface is rocky (crust and mantle),
but they have a metallic core and they have
little or no atmosphere
• They have few or no satellite (Earth has
one, the Moon, and Mars have 2, Deimos
and Phobos)
The eight planets are divided into two groups:
OUTER, JOVINS OR GAS GIANT PLANETS: They
are Jupiter, Saturn, Uranus and Neptune
• They occupy the outer orbits of the solar system
(outside the main asteroid belt)
• They are of enormous size (Jupiter is the largest
of the Solar System)
• They consist mainly of gases (thick
atmospheres), except a small rocky core
• They have great number of satellites (Jupiter
63, Saturn 60 and its famous ring, Uranus 27 and
Neptune 10)

47. MAIN BELT ASTEROID
KUIPER BELT ASTEROID
ASTEROIDS
They are small rock
fragments, grouped in a
narrow strip, although they
orbit independently of each
other around the Sun
There 2 large asteroid belts:
- The Main belt between Mars and Jupiter (therein lies the dwarf
planet Ceres)
- The Kuiper belt located beyond Neptune (in it are the dwarf
planets Pluto and Eris)
Most meteorites that fall to Earth are
fragments of Main-Belt asteroids
Beyond the Kuiper belt is the Oort
Cloud: A set of bodies formed by ice,
methane and ammonia.
While the Oort Cloud, has not been
observed directly (a body at those
distances is impossible to detect even
with X-ray), astronomers believe it is the
source of all comets like Halley.

48. COMET HALLEY: It is a short-period
comet because it passes near Earth
every 76 years. The last time It passed
near the Earth was in 1986 (it will pass
again in 2062)
HALEY COMET ORBIT
COMETS
These celestial bodies are very rare since they have a highly
eccentric orbit and are only visible when they approach the Sun,
which they do every so many years because they come from the
limits of the Solar System (the Oort Cloud). When they are away
from the sun, the comet’s nucleus is formed by ice, dust, methane
and ammonia in solid due to low temperatures. As they approach the
Sun the temperature rises and their components begin to melt and
evaporate, leaving a trail dust along its path forming the tail of the
comet. Each time they pass near the Sun they lose a fraction of its
mass
The comet's
tail is always
oriented away
from the Sun
because the
Solar wind
pushes it out.
The last comet seen from Earth
was the Hale-Bob in 1997. It could
be seen for several nights in the
sky, but its return period is 2,500
years, so that we will not see it
again until 4497. It’s a long-period
comet.
Hale-Bob

49. A shooting star is a small dust or small rock (called also meteoroid) of
about a few millimeters that as entering the upper layers of Earth's
atmosphere, produce a luminous phenomenon by ionization of the air
in its path and by light emission after suffering a sudden high heat.
SHOOTING STARS AND TEARS OF SAN LORENZO
NIGHT
The tears of San Lorenzo night: The story tells that after crucifying Pope Sixtus II,
the Romans wanted to obtain the treasures of the Church. But when the emperor
demanded Lorenzo, responsible for managing and maintaining the property of the
Church in the time of Pope Sixtus II, to deliver the treasures to them, he gathered a
large group of blind, lame and needy people and presented them saying that those
were the property of the Church. The emperor's response was immediate. According
to legend, St. Lawrence was roasted in a kind of grill by Emperor Valerian.
There are dates on which the activity
of shooting stars increases, as is the
case of the Tears of San Lorenzo
night. This is due to the Earth
crossing the orbit of a comet,
where the density of interplanetary
dust is greater.
The comet causing the Perseid is
Swift-Tuttle comet, which visit us
every 134 years.
The saint endured his
martyrdom on 10 August
of 258 year, and for
subsequent nights the
Romans saw hundreds
of shooting stars drawn
in the sky : they were his
burning tears.
Thereafter, the night of
the year with more
shooting stars become
to be called the tears of
San Lorenzo night
(always in mid-August).

50. METEORITES
They are fragments of asteroids or comets that remain travelling
through space at a high speed. They revolve around the sun until they are
attracted by Earth's gravity (or other planets gravity). When they enter the
atmosphere, its temperature increases to incandesce and we see them
as shooting stars. If they are small in size, they disintegrates as they
pass through the atmosphere, but if they are large in size they fall on the
surface forming large impact craters (as such filling the Moon or Mercury)
Depending on their composition are
classified: lititos (rocky, coming from the
asteroid's surface layers) and siderite
(metallic, consisting in iron and nickel from
the core of the asteroid)

51. THE DISAPPEARANCE OF THE DINOSAURS
One of the most popular theories is that the dinosaurs disappeared 65 m.y. ago by the impact of a large
meteorite on the Earth. The strong impact pulverized the meteorite and part of the Earth's surface where it fell,
causing a thick layer of atmospheric dust that covered sunlight for several years. The Earth's temperature
dropped sharply and plants and vegetables disappeared. With it, large herbivores and also carnivores
disappeared, so that only small scavengers and detritivores animals survived, like a rodent like a shrew, from
which all mammals evolved since that time. Finally the atmospheric dust deposited on the ground, sunlight
came to the surface of the Earth again and seeds that were dormant germinated. New organisms appeared and
the Age of Mammals began, replacing the empty niches left by the large reptiles.
An evidence supporting this theory is the crater found in Yucatan
Peninsula (crater Chicxulub), which agrees in size and age with
the one expected according to the theory. Another evidence is the
fact that a thin sediment layer rich in a rare metal, iridium, (rare
on Earth and abundant in meteorites) had been found . This
layer is 65 m.y. old and is distributed homogeneously throughout
the planet's surface.

52. ORIGIN OF THE SOLAR SYSTEM (Theory of planetesimals)
5000 m.y. ago, the materials of a nebula located on the outskirts of
the Milky Way, began to stir and concentrate probably due to the
push of a shock wave produced by the explosion of a nearby
supernova. (figures 1 to 5)
Consequently most of the matter in the nebula, attracted by its own
gravity, condensed and began to concentrate in the central part of
the future planetary system that will be formed. The huge gravitational
force in the central mass compressed and heated the material until the
core temperature reached enough to initiate thermonuclear reactions
that make stars emit large amounts of energy. It was the birth of the
Sun.
The intense solar emissions "blown" into space much of the matter. The
rest remained revolving around the young star because of gravity, to
eventually form an equatorial flattened disk around the Sun

53. In the equatorial flattened disk, denser materials were
placed closer to the center (innermost orbits) and the
lighter ones also did outwards. Subsequently, within the
disk concentrations of matter called planetesimals,
which were arranged in different orbits around the sun,
were shown They began to collide into each other,
destroying and gathering in larger bodies, with more
gravity, that attracted the planetesimals in their
environment. So in each area of ​​the ring, a planet began
to "grow" from planetesimals that met and merged.
The gaseous outer planets were formed first and they
were formed with the lighter elements of the nebula. On
inner zones of the disk were the rocky inner planets
formed with heavier materials. In these rocky planets,
collisions of planetesimals melted down the outside of
these protoplanets generating magma oceans up to 1000
km depth.
Then the planets cooled and created an atmosphere
with the gases released, that were retained only on the
planets which had enough gravity.
Satellites were formed with the remaining material of
planets construction, except for the Moon, which is a
particular case. Far from planets, there are also billions of
comets, icy debris of initial nebula.

54. EARTH AND OTHER PLANETS OF THE SOLAR SYSTEM FORMATION
It is believed that the asteroid belts are planetesimals remnants of a planet that failed to form for unknown
reasons.

55. SOLAR SYSTEM PLANETS
MERCURY
The smallest planet in the
Solar system (its radius is
1/3 of the Earth's radius). It
lacks satellites and
atmosphere.
Its outdoor temperature
undergoes extreme
variations, between 425 ºC
at day to -170 °C at night.
Its surface is covered with
numerous impact craters
from meteorites
VENUS
It has similar size to the Earth and
also its internal structure is
similar (Iron core, rocky mantle and
crust). It is volcanically active,
although it has not been detected
tectonic plates like on the Earth.
Its rotation is opposite to the other
planets.
Its atmosphere is mainly carbon
dioxide, so that the greenhouse
effect is very powerful and its
average surface temperature is
480 °C.
EARTH
It is the only planet that has 3/4 of
its surface covered by water. It
has a thin layer of gases that
form the atmosphere, thanks to
which the average surface
temperature is maintained at
about 15°C. This allows existence
of liquid water and life on the
planet. It has a single satellite
(the Moon). Its magnetic field is
exceptionally strong and is the
only planet that has plate
tectonics.

56. MARS
Olympus Mount is the largest
volcano in the solar system with 24
km altitude, the base would occupy
most of the Iberian Peninsula
The Red Planet, about half-size of the Earth. It has 2 small
satellites (Deimos and Phobos). Its light atmosphere is low in
carbon dioxid, therefore it barely possesses greenhouse effect. Its
average surface temperature is -50°C. In its atmosphere it has
detected methane gas that could be produced by organisms. At
some point, long ago it had liquid water because on its surface
there are signs of erosion produced by a watercourse. Currently
there is no water on its surface, although it is believed that there
could be water under the icy poles.
Its surface is the best known so far (it has been explored by
robots: first by the Pathfinder, then by the Spirit and the
Opportunity) and it is the target of the next manned mission. Its
surface is abundant in impact craters and large reliefs indicating
a great external and internal activity. Mount Olympus, the largest
volcano in the Solar System is on it .
Elongated marks on its surface led to
believe in fantastic "channels" built by alien
beings and the existence of Martians and
potential invasions of the Earth. Ex.: The
War of the Worlds by Orson Wells

57. JUPITER
This is the largest planet in the Solar System (Its radius is eleven
times the Earth's radius). It has an intense magnetic field.
Although it has some solid or liquid material inside, it is a purely
gaseous planet. Like the stars, it is made of hydrogen and helium,
but it does not meet the conditions to have nuclear fusion reactions.
On its surface there are huge meteorological formations. The Great
Red Spot is a powerful anticyclone twice the size of our planet.
It has 63 satellites, four major (Io, Europa, Ganymede and Callisto)
were discovered by Galileo in 1610
SATURN
The most characteristic feature of Saturn is that it has over 60
satellites and a peculiar system of rings visible from the Earth,
formed by dust and rock fragments orbiting at its equatorial plane.
These are small-sized particles with plenty of iced water.
Its density is extremely low, even lower than that of water.
Its two main satellites are Titan and Enceladus: Titan has a
methane-rich atmosphere, similar to that of the early Earth and
Enceladus has liquid water a short distance bellow the surface.
Saturn is the
second largest
planet in the
Solar System (it
has a radius of
10 times
greater than the
Earth)

58. URANUS
Uranus has a radius 4 times that of the Earth. Its
main feature is that its axis of rotation is highly
leaned, almost 90° to the plane of the orbit (Its
rotation axis is nearly horizontal with reference to
an ecliptic plane). It's like it revolve lying. This
also produces a singular magnetic field (with a
corkscrew-shaped tail)
It is the coldest planet in the solar system
It has 27 satellites, known so far and a ring
system, darker than those of Jupiter. It is blue-
green due to methane in its atmosphere
NEPTUNE
Neptune has a size slightly smaller than Uranus (its radius is three
times that of the Earth). It’s the farthest planet to our Sun. It was
discovered by mathematical calculations and once given its
position, it was observed with a telescope.
It has 8 satellites and a set of 4 very faint rings. Like Uranus it has
a rocky core (consisting of rocks, ammonia and methane) and an
atmosphere of hydrogen, helium, steam water and methane,
which gives it its blue coulor.
In the atmosphere of Neptune the temperature is below -200°C and it
produces giant hurricanes. Its atmosphere is very dynamic and
changes rapidly. Its winds are the fastest in the Solar System, reaching
2.000 km/h

59. Double Planet is the name that scientists give to
Earth-Moon system because of the excessive size
of the satellite with reference to the planet, only
49 times smaller than the Earth (if the planet were the
size of a basketball, the moon would be like a tennis
ball). It is too large compared to the other
satellites of the Solar System and its
corresponding planets. It is also lower in density
and gravitational force. It lacks atmosphere and the
surface temperature changes from the maximum
daytime of 107°C, to night minimum -173ºC.
THE MOON
Actually, the Moon doesn’t revolve around the Earth,
but the Earth and the Moon revolve around the mass
center of both
Apollo 11 (in 1969)
was the first
manned spacecraft
that reached the
surface. They
collected lunar rocks
and soil samples.

60. As the Earth is a large body, the gravity that the Moon
exerts on it is different at each point: At the nearest
point it is much higher than at the center of the mass of
the Earth, and much lower at the furthest point of the
moon. So while the Earth is rotating around the center of
gravity of the Earth-Moon system, it appears a force that
attempts to deform it, giving it the appearance of an egg.
This phenomenon is called gravity gradient, which
produces the tides. As the Earth is solid, deformation
affects more in the waters and is what gives the effect of
water moving up and down twice a day (rises in the
nearest and farthest points from the Moon and descending
in both middle points). The tide changes every six hours
following the rotation of the Earth.
When the gravity of the moon and sun are added, it
produces a particularly high tides called spring tides and
therefore, an especially low water. When the Moon and
the Sun are perpendicular to each other, tides are
smaller than current, and they are called neap tides
TIDES
An associated effect is that tides slow Earth in its
rotation (there’s a lost of energy due to friction of the
oceans to the bottom of the sea), and since the Earth-
Moon system has to conserve angular momentum, Moon
makes up away 38 mm (aprox.4 cm) each year. It has
been demonstrated by laser distance measurements made
possible by the retro-reflectors that the astronauts left on
the moon.

61. ORIGIN OF THE MOON: THE BIG IMPACT HYPOTHESIS
When it was discovered that the Moon composition was the same as that of the
earth's surface it was assumed that its origin had to come from the earth itself. A
body so large relative to our planet could hardly have been captured, nor was likely
to have been formed near the Earth. Thus, the best explanation to the formation of
the Moon is that it was originated from fragments that remained after a
cataclysmic collision with a Mars-sized protoplanet in the early Solar System
(Giant impact hypothesis). This theory also explains the great inclination of the
Earth’s rotation axis, which was caused by the impact.
The enormous energy supplied by the collision melted the crust to complete and large amount of
incandescent debris flung into space. Eventually, it formed a rocky ring around our planet until, by
accretion, the moon was formed.
Its initial orbit was much closer
than the current one and the
Earth-day was much shorter as
the Earth rotated faster. For
hundreds of millions of years, the
Moon has been moving slowly
away from the Earth, while the
rotation speed of the Earth has
decreased. It’s due to the transfer
of angular momentum that occurs
between the two bodies. This
process continues today at a rate
of 3.8 cm per year.
In a intermediate state, the Earth had also a ring

62. LUNAR RELIEF
After its formation, the Moon experienced a cataclysmic period, dated around 3,800-4,000 million years ago,
in which the Moon and the other inner Solar System bodies suffered violent impacts of large asteroids. This
period, known as late heavy bombardment formed most of the craters observed on the Moon, as well as
in Mercury. The analysis of the surface of the moon provides important data about this final period in the
formation of the solar system. Later there was a period of volcanism consisting in the emission of large
amounts of lava, which filled the largest impact basins forming the lunar seas. This period finished 3,000
million years ago. Since then, little has happened on the lunar surface but the formation of new craters due to
the impact of asteroids
When Galileo Galilei turned his telescope toward the
moon in 1610 he could see two different surface
regions. Ones are dark regions called “seas“ which of
course do not have water, and have names such as Sea
of ​​Serenity and Sea of ​​Fertility. They are plains with few
craters. The rest of the lunar surface is brighter, and
represents higher regions with a high density of
craters, such as Tycho and Clavius. In the lunar surface
there are also mountain ranges, they have names like
Alps and Apennines, as on Earth.
Crater Tycho Sea of ​​Tranquility