Comets and the Moon
While the Moon is our closest neighbor, Comets travel from the very edge of the solar system to visit us.

Lately, we have been visited by some very special comets. Why they are special is because of their brightness. Just over a year ago, Comet Mc Naught, graced our skies, so bright that at it's peak, it could be seen in daylight!
Comets are, normally, not very bright at all, appearing only as fuzzy stars and showing a faint tail in urban skies. Comets are described as blazing a trail across the sky in a night but the reality is that they are in fact dirty snowballs, the leftovers from the formation of the planets, bits of rocks, sandy minerals, frozen gasses, water, even organic compounds.
It's all loosely bound together in a very black sticky crust...
As they get closer to the sun, the suns rays heat up the crust, the gasses frozen inside start to boil away. Jets of gas blast dust and even small rocks out of the comet. A cloud of gas forms around the comet, we call it the coma.
The suns out flowing solar wind, blows the coma back and away from the comet it's self, this forms the tail.
Some times we see a second tail that's Blue in colour. Here the gasses leaving the comets Nucleus, have been ionized by the suns radiation, the ionizing gasses from this straight blue tail...

Comets Move slowly across our sky, sometimes taking many months to cross from one side of the sky to the other. You only notice that each night, if you check closely, that against the backdrop of stars that movement from night to night is taking place.
While they travel, they lay a trail of sand and rocks that hangs there in space. If the trail of debris is laid across the path of the Earths orbit, we, on the Earth wiz through this dust trail,... as the dust collides with our atmosphere it burns up in a spectacular streak of light...
A Shooting star!

If we get a comets rock, it may even make it through the atmosphere and strike the ground.... A Meteorite!
Not all Meteorites are from comets but a large proportion are...
About every 50,000 years an entire comet may hit the Earth. Although this could be devastating to life here, it happens quite often when you look at our history. Some even think that Organic compounds found in comets may have carried the building blocks of life to Earth billions of years ago and that even today, many Viruses rain down through our atmosphere that are born of comets soup of organic material.... this would suggest that viruses are the product of space!!!?

Over the eons of human history, Comets have been seen to foretell of disaster (Latin for evil-star) or even great victories and the like. Odd how the human race looks to the misunderstood skies for answers.....
Every year we may find about a dozen new comets. Most are too faint to see with the un-aided eye but as the pictures here show, some are very spectacular indeed.

Click here to go to "The Moon"...
Comet McNaught image source AAT siding spring.
Comet McNaught so bright for the southern hemisphere early 2007 and now below, Comet Holmes captures the imagination of northern hemisphere people at the start of 2008... what will 2009 have in store??? the fact that we had two such bright comets in two years is incredible!
A very rare event!  Images AAT.

Comet Holmes, image source AAT Siding Sping

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