METEORITES

A meteorite is a meteor-like body in space. It is large enough to reach the earth's surface without burning up in the atmosphere (unlike a meteor). While falling, a meteorite leaves a bright trail in the sky. This trail is known as a ire-ball. It is hard to locate a meteorite even if the trail is followed because it looks just like an ordinary stone. So, it cannot be easily distinguished.

A meteorite may be made of metal (iron and nickel) or stone. It may be a fragment from colliding asteroids. In 1908, a meteorite –Tunguska crashed on the ground in Siberia. Its blast was felt by people up to a distance of 80 kilometers.

Scientists collect meteorites to study their material in order to know more and more about the material of which planets are made.

When a meteorite crashes on the earth, it causes a crater-deep pit-that may be several kilometers across. The meteor-crater caused by the smashing of the meteorite Barringer is 1265 meters across and 174 meters deep. It can be seen in the Arizona Desert in USA.

COMETS

Comets are believed to be left-over particles of the gas cloud that formed the solar system. This left-over gas cloud contains billions of icy lumps. Each lump is a comet with a nucleus made up of crumbly rock-particles trapped inside a frozen liquid.

Any time a comet may be knocked off its normal course and move towards the sun. Getting near it, its outer icy part melts and boils away into vapor. As for the solid inner part, it is released of the icy trap as dust. Thus the comet forms an enormous head with a long tail. As it travels in space, it sheds bits of itself. The picture given above clearly shows a traveling comet. When the comet travels away from the sun, its tail gets shorter and it again becomes a snowball. Moreover, it always travels tail first.

HALLEY'S COMET

The English scientist Edmund Halley (l656-1742) A. D. became famous for his research on comets. He proved that the comets seen in 1531 A.D., 1607 A.D. and in 1628 A.D. (which he himself saw) were the same one comet. He predicted that it will be seen in 1759 A.D. again and it happened so. So, it was named Comet Halley. Remember that this comet has been seen in 1835 A.D., 1910 A.D. and 1986 A.D. again and again. According to Halley, it will be seen 2300 times more and then decay.