2. Agenda
1. Comets
2. Comet Makeup
3. Comet Orbit
4. Comets in History
5. Halley’s Comet
6. Conclusion
7. Bibliography
Southern Arizona in 1986
3. Comets Fast Facts• *Dirty Snowballs – Fred
Whipple (icy dirtballs)
• Small icy solar system body
that outgasses: when
ORBITINGTHE SUN
• Dust, ice, carbon dioxide,
ammonia, methane, and
more!
• Left over from the formation
of stars & planets billions of
years ago
4. Physical Characteristic
• Solid nucleus (core) mostly ice, dust,
frozen water, ammonia, carbon dioxide,
carbon monoxide & methane
• As comet approaches the sun nuclear
surface turns into gas forming a cloud
known as a COMA
• Solar radiation pushes particles away
formation of DUST TAIL
• Charged particles convert some gases
into ions ION TAIL
6. More about the Makeup
• Most comets nuclei measure 16 km
(10 miles)
• Some comets have tails that can
reach 1.6 million km (1 million miles)
wide
• & tails reaching 160 million km (100
million miles) long
• Comets are visible with the naked
eye when they pass close to the
sun comas & tails reflect sunlight &
glow energy absorbed from sun.
10. Orbital Characteristic
• Comets are classified based on the
duration of their solar orbit
• Short-period orbit 200 years or less
• Long-period orbits more than 200 years
• Single-apparition comets not bound to
the sun, orbit out of the solar system
• Scientist have found comets in main
asteroid belt might be key source of
water for inner terrestrial planets
• Long-period comets thought to come
from Oort cloud
11. Oort Cloud
• Spherical cloud of
predominately icy
planetesimals
• Surrounds the Sun up to
50,000 AU, almost a light-
year
• Astronomers believe
cloud formed closer to
sun, and was scattered
out by gravitation effects
from the giant plants
12. Halley’s Comet
• Arguable the most famous comet
in the world
• Visible to the naked eye every 76
years roughly (if your lucky it might
appear twice in your lifetime)
• Last appeared in 1986 first time
technology allowed for in depth
study
• Next appear in mid 2061(if you are
20 know, you’ll be 68)
13. A Bit of Halley History
• Halley’s comet records date
back to 240 BC
• In clear records of the Chinese,
Babylonians, and medieval
Europeans
• PERIODICITY first determined in
1705: English Astronomer
Edmond Halley
14. 1986
• First time we has the technology to
get close to the comet
• When it passed earth in 1986: 5
spacecraft's flew past it & gathered
unprecedented detail
• First time close enough to look past
coma and study nucleus
• Nucleus was equal parts ice & dust
• 80% of ice water
• 15% carbon monoxide
16. Important Take Always
• Comets: Ice & Dust balls left over from star &
planetary creation billions of years ago
• Most orbit the sun & when they get close,
nucleus heats up and forms a gas atmosphere
called a coma
• The solar radiation pushes dust & gas off form
dust & ion tail
• Halley’s Comet “Comet of Earth”
• Visible to the naked eye every 76 years
• Hopefully in 2061 we will ALL see Halley!!
