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Asteroids, Comets, Meteors…what’s the difference?
Astronomy
Name:
Period:
Asteroids Word Bank:
planetoids
years
Sun
gravitational
Mars
km
orbit
belt
asteroid
Moon
coalesced
Asteroids are rocky or metallic objects, most of which orbit the ________________________ in
the asteroid belt between the planets ________________________ and Jupiter. A few asteroids
approach the Sun more closely. Asteroids are also known as ________________________ or
minor planets. The first ________________________ discovered (and the biggest) is named
Ceres; it was discovered in 1801.
About 3,000 asteroids have been cataloged. Asteroids range in size from tiny pebbles to about
578 miles (930 kilometers) in diameter (Ceres). There are about 40,000 known asteroids that are
over about 0.5 miles (1 ________________) in diameter in the asteroid belt. Sixteen of the 3,000
known asteroids are over 150 miles (240 km) in diameter.
The asteroid ________________________ is a doughnut-shaped concentration of asteroids that
orbit the Sun between the orbits of Mars and Jupiter, closer to the orbit of Mars. Most asteroids
orbit from between 186 million to 370 million miles (300 million to 600 million km or 2 to 4
AU) from the Sun. The asteroids in the asteroid belt have a slightly elliptical
________________________. The time for one revolution around the Sun varies from about
three to six Earth ________________________. The strong ________________________ force
of the planet Jupiter shepherds (guides) the asteroid belt, pulling the asteroids away from the
Sun, keeping them from falling into the inner planets.
The asteroid belt may be material that never ________________________ into a planet, perhaps
because its mass was too small; the total mass of all the asteroids is only a small fraction of that
of the Earth's ________________________. A less satisfactory explanation of the origin of the
asteroid belt is that it may have once been a planet that was fragmented by a collision with a
huge comet.
Comets Word Bank:
Halley's
km
solar wind
orbits
nucleus
Sun
slows
Earth
atmosphere
elliptical
vaporizing
tail
gases
A comet is a small, icy celestial body that ______________________ the Sun. Comets are made
up of a ______________________ (it is solid ice, gas and dust), a gaseous coma that surrounds
the nucleus (it is made of water vapor, CO2, and other ______________________) and a long
______________________ (made of dust and ionized gases). The long tail of gas and dust
always points away from the ______________________, because of the force of the
______________________ (a continuous stream of electrically charged particles - ions- that are
given off by the Sun). A comet's tail can be up to 250 million _______________ long, and is
most of what we see of the comet. Some well-known comets are ______________________,
Shoemaker-Levy 9, Hale Bopp, and Swift-Tuttle.
Comets orbit the Sun in highly ______________________ orbits. Their velocity increases
greatly when they are near the Sun and ______________________ down at the far reaches of the
orbit. Comets are light only when they are near the Sun (when the gas is
______________________); comets are dark (virtually invisible) throughout most of their orbit.
We can only see comets when they're near the Sun.
The ______________________ passes through the orbit of some comets. When this happens, the
left-over comet comet debris (rocks, etc.) bombards the Earth, and the debris burns up in our
______________________. This is called a meteor shower; in it, many meteors fall through the
atmosphere in a relatively short time.
Meteors Word Bank:
shower
heat
brighter
meteor storm
meteorite
atmosphere
space
surface
rock
time
burns
meteor
shooting
Mars
asteroids
Meteoroids are small bodies that travel through _______________________. Meteoroids are
smaller than asteroids; most are even smaller than a pebble. Meteoroids have many sources, but
most come from asteroids that are broken apart by impacts with other
_______________________. Other meteoroids come from our Moon, from comets, and from the
planet _______________________.
A _______________________ is a meteoroid that has entered the Earth's atmosphere, usually
making a fiery trail as it falls. It is sometimes called a _______________________ star or a
falling star (but it is not a star). The friction between the fast-moving meteor and the gas in the
Earth's atmosphere causes intense _______________________; the meteor glows with heat and
then _______________________. Most meteors burn up before hitting the Earth. A fireball is
any meteor that is _______________________ than Venus (magnitude -4). A meteor
_______________________ is a phenomenon in which many meteors fall through the
atmosphere in a relatively short _______________________ and in approximately parallel
trajectories. A very intense meteor shower is called a __________________________________.
A _______________________ is a meteor that has fallen to the _______________________ of
the Earth. These rare objects have survived a fiery fall through the Earth's
_______________________ and have lost most of their mass during the trip. Meteorites are
made of _______________________ and/or metals.
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