Transcript Comets, Asteroids, Meteors and the things beyond Neptune!

Comets, Asteroids, Meteors
OH MY!
What’s the difference?
• Comets- small body of ice and dust in a
highly elliptical orbit around the Sun.
• Asteroids- Large rocky body (≥ few
hundred meters in diameter) that orbits
the Sun.
• Meteoroids- small rocky body (< few
hundred meters) in orbit around the Sun.
ALL ARE PLANETESSIMALS! Left over from
the formation of our solar system
Comet Hale-Bopp 1997
Comet Diagram
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Dust tail is opposite the motion of the comet. Trail of debris left behind.
Ion tail is ALWAYS on the opposite side of the Sun. Solar wind
(charged particles, electron and protons, shot outward from the Sun).
The charged particles excite the gases emitted from comet and give off
light (usually blue).
Both tails get bigger/brighter the closer to the sun.
– Dust tail because the sun warms the comet, sublimating the gases and
allowing more debris to fall off.
– Ion tail because more charged particles from the sun are colliding with
increasing gases given off from the comet.
Orbit
•The orbit of comets are highly
eccentric (elliptical)
•UNLIKE asteroids and planets,
the orbit is not necessarily on the
same plane as the path planets
take around the Sun.
•Long Period comets orbit Sun
over 100 yrs
- Hale Bopp 2600 yrs.
•Short Period less than 100
- Haley's comet 76 yr. (2062)
- Comet Encke shortest
orbital period 3.3 yrs.
Comet Hyatuke 1996
Composition
• Dirty Snowballs
– Mostly rock and ice surrounded by solid H2, water,
CH4, CO, O2, which sublimate (solid to gas) when
approach the sun.
– Recently found CaCO3!!!
• Missions:
– Deep impact. Study the nucleus of Comet Temple 1.
Detonation was July 4th, 2005.
– Stardust. Followed comet Wilde 2 and collected
comet dust. Returned to Earth Jan. 15, 2006
• Dust Tails leave a trail of debris. If the Earth
passes through debris we get a meteor shower.
• Surface of Comet
Temple 1
– Taken from the
Deep Impact
Mission
Artist conception of what comet
looks like as it approaches the Sun
• Surface is covered with jets of gas as they sublimate
(turn from solid to gas) from the warmth of the Sun.
• Notice the “floating” rocks. Comets have very little
mass, compared to a planet, and therefore have very
little gravity.
Meteors
“Shooting stars”
• Dust-like comet fragments that enter our
atmosphere at high speeds. 10 to 50 mps
(up 180,000 mph)!
• They leave a brief flash called a train in
the upper atmosphere. caused by gases
becoming charged in our atmosphere
• Usually the size of sand or less.
• Fireball- long lasting shooting star (few
seconds). Usually basketball size or more.
Fireball during Leonids
(Mid-November)
Another, cooler looking, Fireball
Meteorites
• Meteors that make it to the ground.
• kinds
– Stoney- mostly rock (feldspar) (called
chondrites)
– Iron- metal mix
• Largest ever found
– Hoba meteorite. Over 50 tons.
Largest Ever
•Most meteorites
slow to terminal
velocity due to air
friction. 150 to 200
mph (depending on
mass)
•If they are traveling
at greater speeds, it
will result in craters
on the Earth’s
surface.
APOD Nov. 2002
•*** This guy made the mistake of calling
NASA. They took the meteorite worth quite
a bit of money. SO, he sold his car on ebay
and got way more than it was worth.
The Meteor Crater
99% + of projectile is vaporized
if they are over 50 tons.
If less, they slow to term. vel.
2000 meter crater (roughly 1 mile)
20:1 ratio
50,000 yrs old
Chicxulub Crater
Yucatan Pennisula
• 120 Mile wide
crater formed
from a 6 mile
wide asteroid.
• Marks the end of
the MesozoicKilled 70% of
ALL species
(including dinos)
• Mostly buried
today.
Meteor Showers
• Increased count per hour.
– On a normal day you should see 1/hour.
– During a shower, up to 100/hour
• When Earth travels through dust trail left behind
by comet (from dust tail). OR ejecta from meteor
collision on another planet.
• Name after constellation they appear from.
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Perseids- Aug 10-13
Leonids- Nov. 16-17
Geminids- Dec. 10-15
Many more
Leonids 1998
Asteroids
• “Minor Planets”
• Found in 2 belts.
– The Asteroid Belt (1/2-way btwn Mars & Jup)
– Kuiper Belt: Beyond Neptune… includes
Pluto, Xena & Sedna. A few bil miles to 10’s
of billions of miles.
• Mostly orbit on same plane as planets, but
finding more and more that don’t.
Surface of Asteroid Itokawa
Oort Cloud
• Beyond Kuiper belt. Home to trillions of
icy/rock objects up 5 trillion miles away
(almost a lightyear).
• Cannot see these objects yet, but it is
believed there could be objects as big as
the Earth.
• We see 10 or so comets a year originating
from the Oort cloud.