OAS NOVEMBER 20013 ASTRONOMY EZINE VOL 2 | Page 25

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us forms a thin atmosphere around it called the ‘coma’, the energy from the sun
acts on the coma forming a tail. While the nucleus can be up to 60 km across the
coma can be as big as the sun, and the tails can stretch for thousands of kilometres. The Coma and tail have a high albedo, the ices, gases and water are now
very reflective which for astronomers is a good thing as we can now observe the
comet. One thing to mention the tail points away from the heat source.
Comet - Chemical Composition
It is possible that comets were responsible for bringing water and life to planet
earth. Astronomers and scientists now know there is plenty of water out there in
the cosmos be it in a frozen state and as hard as rock. However comets are made
up of frozen gases too. These gases include carbon monoxide, carbon dioxide,
ammonia and methane. Other properties include compounds such as methanol,
hydrogen cyanide, formaldehyde, ethanol and ethane. Comets also can contain
more complex molecules such as amino acids (building blocks of life) and long
chain hydrocarbons.
Comet ISON (C/2012 S1)
Discovery: 21st September 2012 by two Russian astronomers working for the the
International Scientific Optical Network, their names are Vitali Nevski and Artyom
Novichenok.
Dubbed the comet of the century, ISON could be a truly spectacular comet. On
the 1st October 2013 @ 17:27 UTC ISON made its closest approach to Mars, and
passed within 6.74 million miles. Through October it has an average speed of
78,717 mph and will continue to accelerate until the 28th November where it will
speed up around the sun to a staggering 845,000 mph.
Size: Approx 3 miles in diameter, conclusion from data analyzed by NASA’s swift
satellite.
Viewing
The comet will pass within 1.2 million miles of the suns surface on the 28 th November 2013 when it reaches perihelion. On its outward journey it will pass over
the Earths northern hemisphere at a distance of 40,000,000 mile on the 26 th December. If estimates are correct you should be able to observe the comet with the
unaided eye anywhere between November 28th 2013 and January 2014, depending on your location.
Clear Skies!
Dave Bood
Sources NASA, www.cometison2103.co.uk
Image by Hubble Team.
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