• Question: When halley's comet passes earth is it the same comet each time?

    Asked by anon-150745 to Daniel, Hannah, Maggie, Ry, Scott on 9 Nov 2017.
    • Photo: Scott Melville

      Scott Melville answered on 9 Nov 2017:

      Great question!
      Yes, it is the same comet. It’s actually orbiting the Sun, just like the planets are. But instead of a nice, almost circular, orbit – it actually goes around in a really narrow squashed oval. So it takes about 75 years to do one orbit (if you lives on the comet, one year would be 75 times longer), which is why we only see it in the sky occasionally 🙂
      http://cse.ssl.berkeley.edu/SegwayEd/lessons/cometstale/frame_orbits.html

    • Photo: Hannah Middleton

      Hannah Middleton answered on 9 Nov 2017:

      Yes it is the same comet! It is in an eccentric orbit which means its path is more like an oval than a circle, just like Scott said. So it spends most of its time in the outer regions of the solar system, and we only get to see it from the Earth at certain points in its orbit. Comets only have their tails when they come close to the inner solar system, because they get heated up as they get nearby the Sun and some material gets pushed off into the tail. So comets are much more visible when travelling through the inner parts of the solar system not only because they are closer to the Earth, but also because they form big tails.
      Halleys comet was last seen in 1985/1986, so the next time it will be back is around the year 2061.

    • Photo: Ry Cutter

      Ry Cutter answered on 9 Nov 2017:

      Both of the answers given are fantastic so I’ll give you some facts about Halley 😛
      He was the person who first predicted mathematically the orbit of the comet he is now named after. He was also the first person to map all the stars in the whole sky… on both sides of Earth. Halley did a lot of work in mathematics, geometry, geophysics, and astronomy and has had loads of stuff named after him. Including a crater on the moon and on mars!
      Great question
      Ryan

    • Photo: Maggie Lieu

      Maggie Lieu answered on 10 Nov 2017:

      Yup its the same comet, because comets orbit our sun just like planets do, so we will always see them again. Halley comes back around every 75 years. Its only so famous because we can see it with the naked eye, but I much prefer comet Encke who visits every 3 years or so. You’ll need a telescope to see it though!

Comments

  • Photo: anon-150745

    anon-150745 commented on :

    so halleys comet doesnt get any smaller as it orbits the sun?

    • Photo: Scott

      Scott commented on :

      Good question! Maybe it loses a little mass – but all of the gas and little crystals which come off the comet, if you compressed back down to a solid again, would probably not be a significantly fraction of the whole comet (e.g. water expands by about 1600 times when it boils into steam). It’s also picking up some mass as it flies around (little rocks crash into it and stick), so that probably also keeps it’s total mass roughly constant.