More than 5,000 asteroids have been discovered, and most are found between Mars and Jupiter. Comets are made up of frozen dust and gases, and have been described as large, dirty snowballs with icy centers. They often travel on extremely elongated orbits around the Sun. Some comets have orbits that take just 10 years to circumnavigate while other comets have orbits that take hundreds of thousands of years to circulate. The tail of a comet, called a coma, forms when the comet comes within 100 million miles of the Sun.
Meteors are fragments of comets, planets, moons, or asteroids that have broken off.
It is estimated that a billion meteors enter our atmosphere every day. Contact with our atmosphere causes most to disintegrate before reaching Earth. Those that do not disintegrate completely but fall to Earth are called meteorites. Stars are composed of intensely hot gasses, deriving their energy from nuclear reactions going on in their interiors. Our Sun is the nearest star.