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.

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

• 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

Comet Hyatuke 1996

•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.

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

APOD Nov. 2002

•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. •*** 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.

2000 meter crater (roughly 1 mile)

20:1 ratio

50,000 yrs old

The Meteor Crater

99% + of projectile is vaporized if they are over 50 tons.

If less, they slow to term. vel.

Chicxulub CraterYucatan Pennisula

• 120 Mile wide crater formed from a 6 mile wide asteroid.

• Marks the end of the Mesozoic- Killed 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.– 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.