• Question: how and why are comets formed? what are they?

    Asked by 425spaa38 to Jane, Heather, Helen, Hugh, Julian on 11 Nov 2014. This question was also asked by Jxrdan.
    • Photo: Julian Onions

      Julian Onions answered on 11 Nov 2014:

      Comets are mostly left over bits of the solar system that didn’t form planets.
      They are described as dirty snowballs, as they are made of ices and frozen gasses. There are a lot of them orbiting outside the solar system in the Oort cloud, where occasionally a passing star will disturb some of the bits and send them zooming in towards the Sun.
      There is another collection that orbit around between Jupiter and the Sun, they come around more regularly. They are a similar composition though.

    • Photo: Helen Johnson

      Helen Johnson answered on 11 Nov 2014:

      We currently believe that comets come from far out in our solar system – from the Oort cloud or Kuiper Belt. Comets are basically just small objects made from ice, frozen gases and rock. When they approach the Sun, their outer layers burn up and form a stream of gas and dust – their tail!
      There is a mission called Rosetta, which has been travelling out to a comet called 67P for almost 10 years, and is due to land a probe on the surface – TOMORROW! It’s really exciting. Here is a brilliant youtube video.. https://www.youtube.com/watch?v=AvkPFXdpOQQ

    • Photo: Heather Campbell

      Heather Campbell answered on 12 Nov 2014:

      Just to add, the Rosetta should help us answer if water was brought to planet Earth from a comment. Its landing craft should land tomorrow (fingers crossed) and you can watch live updates on http://www.esa.int/Our_Activities/Operations/Live_updates_Rosetta_mission_comet_landing

    • Photo: Hugh Osborn

      Hugh Osborn answered on 12 Nov 2014:

      Comets are lumpy blobs of ice and rock that were left over after the formation of planets. Millions of them were given a gravitational kick from the other planets onto these long, slow orbits. However, they occasionally plummet back into the centre of the solar system where the Sun heats them up so much they give off a tail of gas and dust (and sometimes disintegrate entirely!).

      But there are lots of things we still don’t know about comets. That’s why we’re landing on one TODAY. The Rosetta probe is on it’s way to the surface of Comet 67P, where it will use a handful of instruments to analyse the surface chemistry. That will tell us so much more about these incredible lumps of snow.

      You can follow the landing here http://new.livestream.com/esa/cometlanding!

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