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ANCIENT BELIEFS:
Some people of the ancient world believed
that a comet blazing through the sky was the soul of a hero or a
King on its way to the heaven.
Another belief was that the comets were messengers
of widespread disease and doom.Superstitious people believed that
the tails of the comets were made up of gases and that if Earth
were to pass through the tail of a comet, all life on the Earth
would die.And when the Earth really swept through the splendid tail
of the comet Halley in 1910, enterprising merchants had started
selling comet pills as a protection against disaster.
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WHAT ARE COMETS MADE OF?
Cometary orbits around the Sun are often
exaggerated ellipses. Comets develop tails only when they get so
close to the Sun that material is blown or boiled off them. Each
comet has two tails, one consisting of dust and the other of plasma,
or ionized gas.The dust tail is usually yellow as it reflects sunlight.
The ionized gas tail is often bluish. Tails reach their maximum
brightness at the comet's perihelion, the point of closest approach
to the Sun. At the aphelion, comets are merely lifeless lumps of
dust and ice. One of the most marvelous sights in the night sky
is a large Comet, with its bright head and long glowing tail. Not
until the late sixteenth and seventeenth Century were their paths
studied with astronomical precision.
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Most of the comets are named after the greater
discoverers. Independent confirmation of the elliptical orbits of
the comets finally came in 1758 when the bright comet of the 1680
returned as predicted by Edmund Halley, the great English Astronomer(1656-1742).
Halley's Comet as it has come to be
called, has made many appearances since.On its last passage close
to the Sun in 1986, it was investigated by a number of space probes,
one of which peneterated the comet itself.This comet was visible
to the naked eye from Mumbai in 1987.
Sir Edmund Halley had predicted that
the comet Halley will reappear every 76 years.Comet Wilson came
close to the Sun during April 1987 and was brighter than comet Halley,
the head of Halley's comet, in a computer-processed image made from
photographs taken in 1910, appears to have a three dimensional form.
The bright arcs of gas in front of the head make up the comet, a
glowing halo surrounding the nucleus.The comet is made of water
molecules ionized by the Sun's ultraviolet radiation.
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Image:Halley's Comet
Source:Unknown
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