Section 28.4 Asteroids, Comets and Meteoroids

• Left over from nebula from when the solar system was formed.

• Travel in some type of orbit..

•  

•mixture of ice, frozen gases and dust

•

• nucleus (solid – rock, metal and ice)• coma (cloud of gas and dust surrounds nucleus) • tails (dust and ionized gases). Always points away

from the sun

•

Orbits of Comets

• Highly elliptical• Velocity increases

greatly when they are near the Sun

• Visible only when near the sun

• Dark and virtually invisible throughout most of orbit

Why are comets important?

• Contain leftover materials that formed the planets and the Sun more than 4.5 billion years ago.

• Contain many of the organic materials thought to be essential for life

Origin of Comets

1. Kuiper Belt – short period comets – up to 200 years

Origin of Comets

2. Oort Cloud long period comets – up to 30 million years.

2013 Meteor Showers

NASA's Hubble Space Telescope took this photo of Comet ISON on Oct. 9, 2013, when the comet was inside Mars’ orbit and about 177 million miles from Earth. The nucleus of ISON appears to be intact.

http://www.jpl.nasa.gov/comet/pach17.html

Meteor Showers• Earth passes through the

orbit of some comets• comet debris burns up in

Earth’s atmosphere.• predictable time each

year.• named after the

constellation they seem to originate from

• Rocky or metallic objects

• Most orbit the Sun in the

asteroid belt between Mars

and Jupiter.

• 40,000 known asteroids that are over 0.5 miles in diameter in the asteroid belt

• range in size from tiny pebbles to about 578 miles in diameter

Asteroid Eros

Meteoroids

• small asteroid.

• Usually less than 1 mm

Meteor

• METEOR - meteoroid that enters earth’s atmosphere. Most burn up as a shooting star.

Meteor Crater

Meteorite

• Meteor or part of a meteor that does not burn up entirely and falls to the ground.