Comets are small icy bodies made up of dust and frozen gases like water, carbon dioxide and methane. As comets approach the sun, solar radiation causes their icy cores to heat up and release gases that form tails of dust and ions. The document focuses on Halley's Comet, one of the most famous comets that orbits the sun every 76 years. In 1986 it passed close to Earth and spacecraft were able to study its icy nucleus up close for the first time. The comet's periodic orbit was first determined in 1705 and it has been observed by many ancient civilizations throughout history.

1. Comets &
Halley’s Comet
By: Jennifer Wotczak

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

5. Quick Picture

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.

8. Let’s Talk Orbit

9. More about Orbit

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

15. Quick Video
• https://www.youtube.com/watch?v=C8zV1xiGqf4

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!! 

17. Thank you!

18. Bibliography
• https://solarsystem.nasa.gov/planets/profile.cfm?Object=Comets
• http://www.space.com/53-comets-formation-discovery-and-
exploration.html