Bodies in Our Solar System
Objectives
• Explain why comets, asteroids, and meteoroids
are important to the study of the formation of the
solar system.
• Describe the similarities of and differences
between asteroids and meteoroids.
• Explain how cosmic impacts may affect life on
Earth.
I. Comets
A. Comet Tails When a comet
passes close enough to the sun,
solar radiation heats the ice so
that the comet gives off gas and
dust in the form of a long tail.
B. Comet Orbits The orbits of
most planets are close to perfect
circles, but the orbits of comets
are very elongated.
C. Comet Origins Many
scientists think that comets come
from the Oort cloud, a spherical
region that surrounds the solar
system.
II. Asteroids
A. What Are Asteroids? Small,
rocky bodies that revolve around the
sun are called asteroids.
B. Types of Asteroids There are
three main types of asteroids: Dark
reddish brown to black asteroids,
dark gray asteroids rich in carbon,
and light gray asteroids that have a
stony or metallic composition.
III. Meteoroids
A. Meteor Shower Meteor showers
happen when Earth passes
through the dusty debris that
comets leave behind.
B. Meteoroid: a relatively small,
rocky body that travels through
space.
C. Meteorite: a meteoroid that
reaches the Earth’s surface
without burning up completely.
D. Meteor: a bright streak of light
that results when a meteoroid
burns up in the Earth’s
atmosphere
III. Meteoroids
• E. Types of Meteorites The three major
types of meteorites—stony, metallic, and
stony-iron meteorites.
IV. The Role of
Impacts in the Solar
System
A. Future Impacts on
Earth? Scientists estimate
that impacts that are
powerful enough to cause a
natural disaster might
happen once every few
thousand years.
B. The Torino Scale The
Torino scale is a system that
allows scientists to rate the
hazard level of an object
moving toward Earth.
Fact of the Week
Everyone knows the beloved endangered
kiwi is a flightless bird. As if to make up
for its winged impotence, the kiwi is
actually a violent, temperamental little
bird. But its quirks don’t stop there. The
only bird with whiskers is also distinctly
dog-like in its ability to sniff out food and
threats. In fact, it has the most highly
developed sense of smell of any bird,
lifting its “nose” (beak) into the breeze to
determine its surroundings, just like a dog
would. That’s probably because kiwis are
also the only bird to have prominent
nostrils. Contrary to popular belief, the
kiwi does have wings, but they are tiny
and difficult to detect under the loose,
fluffy, hair-like feathers. The kiwi has
many other unusual characteristics: the
eggs are relatively huge, being one-fifth
the bird’s weight; kiwi pairs mate for life –
as long as 30 years – but tend to have
feisty relationships; the females are larger
and more dominant than the males. In
fact, daddy kiwis incubate the young
while mom hunts – for an unheard-of 80
days, no less. Kiwis are related to
ostriches and emus.