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.