• Question: What is the radius of the milky way?

    Asked by ryzeer to Colm, Eoin, Joseph, Lauren, Stephen on 13 Nov 2013.
    • Photo: colm bracken

      colm bracken answered on 13 Nov 2013:

      The milky way is a typical spiral galaxy with a radius of about 70,000 light years. One lightyear is 9460528400000000 metres, so the radius is about
      1000000000000000000000 metres. This is why we use the unit of light years, otherwise we spend all our time writing zeros.

    • Photo: Stephen Scully

      Stephen Scully answered on 13 Nov 2013:

      Distances are massive in astronomy and therefore we use several special measurements for distance. In this case we use a “Light-Year”, which is the distance light travels in 1 year.

      Light is the fastest thing in the universe and travels at a speed of 300,000 km per second. In one year this distance is about 10,000,000,000,000 km which is 10 million million km.

      The Milkyway is about 100,000 light-years wide. This means it is about 10,000,000,000,000,000,000 km wide. In other words it is about 1 million million million kilometres wide.

    • Photo: Joseph Roche

      Joseph Roche answered on 16 Nov 2013:

      Just in case you meant the radius of the milky way bar of chocolate – it’s about 2cm.

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