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Young World
WORLD OF SCIENCE
Life of a comet
DR. T. V. PADMA
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Comets are some of the fastest objects in the solar system.
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Comets can travel around the sun at about 160 000 km/h (100 000 m.p.h.) making them some of the fastest objects in the solar system. The closer a comet comes in its approach to the sun, the faster it generally moves. The point in a comet’s orbit at which it is closest to the sun is known as perihelion. The point at which a comet (or other orbiting body) is farthest away from the sun is called apehelion. Some comets loop just once towards the sun and then move away, n
ever to return. Some are captured for ever and forced into elliptical (oval-shaped) orbits around the sun. These comets return periodically to light up the earth’s sky. If a comet comes close enough to one of the giant planets such as Jupiter, it may be grabbed by the planet’s gravity. Its path then becomes a loop around the sun at one end and the giant planet at the other.
In the end
To travel from the outer to the inner solar system takes millions of years. Comets that complete their orbits within 200 years are called short period, and those that take longer than 200 years to complete their path around the sun are called long period comets. Comets tend to shrink in size as they make several trips around the sun because the ice melts away. The rocky part of a comet may also be broken up into tiny fragments as it is subjected repeatedly to the pulling power of the sun. Comets may also crash into the sun or collide with a planet and be completely destroyed. This happened with a comet that collided with Jupiter a few years ago. The impact was observed by a satellite deployed by the USA’s National Aeronautics and Space Administration (NASA), which caught an impressive series of pictures showing the impact.
One of the most famous comet seekers of all time is a woman by the name of Carolyn Shoemaker. Shoemaker worked at the observatory on Mount Palomar. She has discovered more comets than anyone alive today.
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