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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.
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.