• Question: How many comets are there in our galaxy?

    Asked by anon-209828 to Verity, Sergio, Nick, Maria, David, Annette on 12 Mar 2019.
    • Photo: Nick Werren

      Nick Werren answered on 12 Mar 2019:


      There are loads of comets in our galaxy, some travel between galaxies and star systems. We think there are just 12 trillion in our solar system alone!

    • Photo: David Whitworth

      David Whitworth answered on 12 Mar 2019:


      In our galaxy? Wow! A lot! As in probably billions to trillions. In our solar system we have so far discovered around 4053, with 14 being discovered this year alone.There is a great website run by the International Astronomical Union (these are the guys that demoted Pluto to a dwarf planet) that keeps track of these things. You can see how many near-earth objects there are 19851, or how many ‘minor’ planets there are in our solar system, 789069, plus all sorts of other things. Go check it out:

      https://minorplanetcenter.net//

    • Photo: Maria Walach

      Maria Walach answered on 13 Mar 2019:


      We don’t know precisely because it’s more than what we can count! Comets are rocks in space with particular orbital characteristics – they go around the Sun but are not bound in the same way as planets are. They usually leave a solar system and eventually come back round to go around the sun before they fly out again!
      We often only really see them as comets when they get close to the sun. That’s when it interacts with the solar wind (a stream of plasma from the sun that moves really fast), which bunches up around it, building a shock front known as a coma! We can see this coma, as well as the trail the comet leaves. The comets are often made of dust or ice, which makes the tail as it comes off the comet and interacts with the solar wind and solar radiation.
      When the comets are really far away, we can’t see this, so it’s harder to count the comets…

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