For those of you interested in comets, now is your chance to see a comet that is visible with binoculars given clear skies and a dark site. Comet 8P/Tuttle has returned to our night skies and is a great opportunity to see a stellar body other than planets and meteors. So let's start off with a little science about comets.
According to the World Book at NASA, comets are 'an icy body that releases gas or dust. Most of the comets that can be seen from Earth travel around the sun in long, oval orbits. A comet consists of a solid nucleus (core) surrounded by a cloudy atmosphere called the coma and one or two tails'.
The origin of short-term comets is believed to be the Kuiper belt situated beyond Neptune - remember that Pluto has been down graded to a dwarf planet which is part of the Kuiper belt. Comets are classed as small bodies within our solar system and are given the name Kuiper belt objects or KBOs. Comet 8P/Tuttle fits into a group of KBOs called 'periodic comets' or 'short-periodic comets'.
Astronomers believe that short-period comets are pulled out of the Kuiper belt due to the gravitational forces exerted on them by the planets and the sun. These objects then gradually create an elliptical orbit through our solar system taking less then 200 years to complete one orbit. It is this orbital pattern that causes comets to leave a tail behind them. As a surface is rotated towards the energy given out by the sun, the surface of the comet begins to melt, exuding gases and dust particles that reflect the visual light waves. Experiments have shown that the gases ejected from comets include, carbon monoxide, carbon dioxide, methane and ammonia. They also eject organic compounds such as methanol, hydrogen cyanide, formaldehyde, ethanol and ethane. It is also theorised that more complex molecular structures such as hydrocarbons and amino acids may also be in existence which make comets a likely origin for life on many planets through comet impacts.
Comet 8P/Tuttle was first discovered and catalogued by Pierre Mechain of France in 1786 however it was the Tuttle brother, Horace Parnell Tuttle, who gave it a name when he observed the comet in January of 1858. The comet is the father of the Ursid meteor shower due to enter the earth's atmosphere between the 1st and 6th of January and is currently observable making its way through Andromeda heading east-south-east passing Triangulum. During much of the first half of January you should be able to spot the comet heading past M33 and down towards the equator where it will come into view for the southern hemisphere observers.
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