Comets, Asteroids, and Meteors. What is a comet?. A comet is a small body which scientists sometimes call a planetesimal. They are made out of dust, rock, gas, and ____. They are kind of like a dirty _________. ice. snowball. Comets are made up of different parts. The nucleus
A comet is a small body which scientists sometimes call a planetesimal. They are made out of dust, rock, gas, and ____. They are kind of like a dirty _________.
The nucleus is the frozen _______ of a comet’s head. It is composed of ____, ____, and dust. The nucleus contains most of the comet’s mass and measure about 10 miles across or less.
The ______ is a spherical blob of gas that __________ the nucleus of a comet. As the comet gets closer to the sun, the heat __________ some of the ice and causes the comet to spew gas and dust particles into space.
The_________and the _______ form the head of a comet.
The _________ is made of ___________ charged gas molecules that are being pushed away from the nucleus by the solar _____. (The blue tail in the picture.)
When a comet is approaching the Sun, the ion tail _______ the comet: when the comet is leaving of the Sun, the ion tail _____. The tail fades as the comet moves far from the Sun.
The _________ develops when the comet is _____ the Sun. This tail is made of small dust particles that have evaporated from the nucleus and are being pushed away from the comet. The tail _______ slightly due to the comet’s motion.
The tail can be up to 250 million km long, and is most of what we see. Comets are only visible when they\'re _____ the sun in their elliptical orbits.
Comet Hale Bopp showing its two tails.
Courtesy of NASA
Surrounding the coma is an invisible layer of __________ that has been released. It is the ___________________ . This cannot be seen from Earth because its light is absorbed by our atmosphere. It is usually between the ion tail and the dust tail.
Comets orbit the Sun in highly _________ orbits. Their speed _________ greatly when they are near the Sun and ______ down at the far reaches of the orbit. Since the comet is light only when it is near the Sun, comets are dark throughout most of their orbit.
Comets originate from either the _______ _____ (beyond the orbit of Neptune) or the ___________ (which surrounds the outer reaches of the solar system.)
Animation of a Comet
ASTEROIDSAsteroids are _______ or _________ objects, also know as____________ or minor planets that revolve around our Sun.
Most asteroids orbit the Sun in the asteroid belt located between _______ and _________. A few asteroids approach the Sun more closely. The asteroids in the asteroid belt have a slightly __________ orbit.
3 to 6
Asteroids range in size from tiny pebbles to about 578 miles (930 kilometers) in diameter.
Some asteroids even have orbiting ______. Here is the asteroid “243 Ida” and its tiny asteroid moon, Dactyl. This is the first asteroid ever found with an orbiting moon. Ida\'s dimensions are about 35 x 15 x 13 miles. Dactyl is only about 1 mile across.
Meteoroids are ______ bodies that travel through space. Most meteoroids are smaller than the size of a ________. Meteoroids are tiny particles left by an asteroid or a comet.
A meteor is a meteoroid that has entered the _____________________, usually making a fiery trail as it falls. It is sometimes called a _________ star or a _______ star.
A meteor shower is a phenomenon in which ______ meteors fall through the atmosphere in a relatively ______ time and in approximately parallel trajectories.
Arizona, November 1966 - The Leonid meteor shower rained 2,300 meteors per minute for 20 minutes. (Photo NASA)
A meteorite is a meteor that has fallen and ______ the Earth. These rare objects have survived a fiery fall through the Earth\'s atmosphere and have lost a lot of mass during that process.
Near Winslow, Arizona, you can visit a crater that was made from a meteorite. The crater is nearly one mile across, 2.4 miles in circumference, and more than 500 feet deep.
Animation on the formation of this crater. http://www.meteorcrater.com/