• Question: Why does a comet have two tails and why do the travel in ellipse shapes?

    Asked by to Alan on 14 Mar 2014. This question was also asked by .
    • Photo: Alan Fitzsimmons

      Alan Fitzsimmons answered on 14 Mar 2014:

      Good question, but this needs a long answer!

      A comet is made mostly of ice, with small microscopic bits of rock embedded within the ice. It also goes around the Sun. When a comet is near the Sun, the ice melts and turns into gas. The gas and bits of rock then get blown back to make the tails of a comet.

      The solar wind from the Sun blows the gas back to make the gas tail of the comet. The solar wind also makes the Northern Lights on Earth, so I’m glad it’s there!

      We call the small bits of rock “dust” because they are so small. Light from the sun pushes this dust from the comet to make the dust tail.

      Did you know I was part of a team that discovered comets have 3 tails? The 3rd tail is made of sodium. You can see a picture I took of this 3rd tail here:
      http://en.wikipedia.org/wiki/Comet_Hale–Bopp#Sodium_tail

      Finally why do comets move around the Sun in ellipses? That’s because gravity keeps them orbiting the Sun. Everything going around the Sun moves in ellipses, even the Earth!

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