The comet that appeared in the sky in November 1680 has two
main claims to fame. It was the first to be discovered by telescope and the
first to have a known orbit.
It was found by accident by Gottfried Kirch, a German
astronomer, when he was actually observing the Moon through his telescope, but as
it approached closer to Earth it became clearly visible to everyone as it streaked
across the sky.
The orbit was calculated by Isaac Newton who made use of his
new theory of universal gravity, publishing his results in his “Principia
Mathematica” in 1687.
The Great Comet was seen twice – once as a morning phenomenon
as it headed towards the Sun and later in the evenings as it made its return
journey towards the outer regions of the Solar System. Newton was the first
person to appreciate that these appearances were of the same comet. It had previously
been assumed that comets travelled in straight lines, passing through only
once. Newton’s discovery that comets travelled round the Sun in parabolic
curves was what enabled Edmund Halley to predict that the comet named after him
would return every 76 years.
Robert Hooke, the English physicist, noticed a stream of
light issuing from the comet’s nucleus. This was the first description of the
emanation of jets of material from active areas.
The Great Comet will not be seen again in the lifetime of
anyone alive today. Its orbit takes it into the outer regions of the Solar System
and it will not return for more than 9,000 years!
© John Welford
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