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Lecture 14

AST101H5 Lecture Notes - Lecture 14: Meteoroid, Kuiper Belt, Oort Cloud

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John Lester

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Chapter 11
Small Bodies Orbiting the Sun
Meteoroids and Meteors
Meteoroids are objects orbiting the sun that are too small to observe
Sizes are from ~1m down to less than 1 mm
Speeds are >10 km/s and faster, much faster than a bullet
When they hit Earth, the friction with our atmosphere heats and vaporizes them, creating
a meteor = “shooting star”, alerting us to their existence
If a meteoroid is large enough to reach the ground without being completely vaporized, it
is called a meteorite
Meteorites can be collected and taken into a lab for analysis
One type of meteorite is made of silicate compounds = “stony” meteorites
Some, called “chondrites”, contain small grains indicating they have not been
heated very strongly
Some are even more “primitive: and contain matter rich in carbon, indicating they
have had almost no heating
They evan contain amino acids that are necessary for life
Another type of meteorite is made of iron
Final type of meteorite is a mixture of iron and stony
These probably also came from the broken up large objects, but are from the
boundary between the stone and iron
Studying meteorites shows us what can happen inside larger objects, maybe even inside
the earth
Aster (star) oid (body) = a rocky body orbiting the Sun that is so small that it looks like a
Another name is “minor planet”
Discovered by observing that they shift their positions compared to the real stars
Before photography they were very hard to notice, but now they’re easy to see
Large asteroid diameter = 530 km
Smallest asteroid’s size ~1 m = meteoroid
About 500,000 asteroids have been observed well enough to derive their orbits and be
given numbers or names
There are millions of asteroids that have not been studied this well
Where are Asteroids Located?
Most asteroids are located in the region between Mars and Jupiter = “asteroid belt”
A small number of asteroids are located in the orbit of Jupiter, 60o ahead of and 60o
behind jupiter = Trojan asteroids
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