Post on 19-Dec-2015
transcript
Asteroids
Astronomy 311Professor Lee
CarknerLecture 15
Quiz #2 Monday
Quiz 2 same format as quiz 1 ~20 multiple choice/matching ~4 short answer
Covers lectures 9-15 bring pencil and calculator No class Friday
Rocks in Space Asteroid -- Meteoroid -- Meteor -- the flash of light when a
meteoroid hits the Earth’s atmosphere sometimes called a falling or shooting star
Meteorite --
Types of Meteorites Meteorites are classified based on their composition Two major types are irons and chondrites
Chondrites are the most common type of meteorite
But, irons are much easier to find
What are the properties of chondrites and irons and how can you identify them?
Iron Meteorites Composed of iron and nickel Often show Widmanstatten
patterns when etched with acid
Widmanstatten Paterns
Chondrite (Stony) Meteorites
Composed of silicates Contain chondrules, small glassy
inclusions of material that were heated and quickly cooled
Carbonaceous chondrites
Chondrules
The Missing Planet In the 18th century astronomers noticed
that there was a gap between Mars and Jupiter with no planets
In 1801 G. Piazzi found a faint moving star in the gap
This is the asteroid belt
The Asteroid Belt
Asteroid Myths
Are the asteroids debris from a planet that exploded?
Is the asteroid belt dangerous to travel through?
Asteroid Facts
Size:
Orbit: Asteroid Belt 2-3.5 AU, some have eccentric Earth crossing orbits
Description:
Formation of the Asteroid Belt
If Jupiter did not exist, a fifth terrestrial planet might have formed at 2.8 AU
Jupiter’s gravity:
Trojans and NEOs Many asteroids are found outside of the
asteroid belt Trojan asteroids have been captured in
Jupiter’s Lagrange points
Some asteroids cross the Earth’s orbit and
are called Near Earth Objects (NEO)
Studying Asteroids
Several asteroids have been observed at close range
In 2005 the Japanese mission Hayabusa studied asteroid Itokawa and tried to collect a sample for return to Earth
Asteroid Features
Only Ceres, Pallas and Vesta (the 3 largest asteroids) have enough gravity to form a sphere
Asteroids show many craters During the heavy bombardment period
asteroid collisions must have been frequent
Composition of Asteroids Asteroids are divided into three
major groups based on composition S Type
C Type
M type
Formation of Asteroids
M and S type asteroids are found in the inner asteroid belt where temperatures are higher
Formation of Meteoroids Some asteroids became large enough to
differentiate
These asteroids were then broken up by collisions
Asteroids that never differentiated formed chondrites
What Use is an Asteroid? Mining
Space Habitats
Spaceships
Providing Material for Life in Space
Summary Asteroids are small bodies that orbit the Sun Most are in the asteroid belt between Mars and
Jupiter (2-3.5 AU) Jupiter’s gravity prevented the asteroids from
forming a planet Description:
Small (most less than 1 km) Max size is few hundred km
Irregularly shaped Heavily cratered
Summary: Meteoroids Iron
made of metal formed from core of
asteroids (M type)
Achondrites (Stony) made of rock with
no inclusions made from crust of
asteroids (S type)
Chondrites (Stony) made of rock with
small inclusions made from
undifferentiated asteroids (S and C type)