Wednesday, 20 August 2014

Wednesday Science Limerick - Comet 67P

There’s a comet named 6 7 P
That Rosetta has wanted to see
And it looks like a duck
Though with plenty of luck
They’ll find water among the debris

Comets are astronomical objects consisting of a mixture of rocks, dust, water ice and frozen gases which orbit the sun in an extended orbit. When they approach the sun they heat up and some of the water and frozen gases evaporate, releasing some of the dust. The escaping material  is blown by the solar wind (caused by plasma escaping from the sun) to form a tail which can sometimes be visible to the naked eye - although the central rocky body is too small to see. Every time it comes close to the sun it loses more material and may break up into fragments. Meteor showers can be associated with some comets - representing small fragment which have become detached and spread out along the orbit over millions of years.

In recent years robotic space craft have approached and photographed comets and at the present time the spacecraft Rosetta is in orbit round the comet 67P/Churyumov–Gerasimenko. (Sorry for the long name - and the fact that I didn't include the full name in my limerick - but comets are named after their discoverers.) It has proved to be most interesting in that it is anything but spherical - and its shape has been likened to that of a rubber duck. Before 1959 it didn't approach the sun closer than about 400 million kilometers but a "close" approach to the planet Jupiter altered its orbit so that it now comes to within 190 million kilometers. Obviously the closer it comes the hotter it gets and the more material it looses each orbit. Some of the smoothest areas appear to be in the "neck" and if the comet consists of two large rocky masses cemented together with water ice it may not be that far from splitting into two. 

There will be much more active research over the next couple of years, with much more detailed photographs plus other scientific measurements of the material escaping from the surface. In addition there will be an attempt to land a probe and sample the surface. I will be following the discoveries with interest and I note that the Wikipedia page is being kept well up-to-date - the last amendment being yesterday.

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