asteroids astronomy 311 professor lee carkner lecture 15

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)