• Question: what is known about the centre of our galaxy (Sagittarius A)

    Asked by Oliver Johns to Heather, Helen, Hugh, Jane, Julian on 14 Nov 2014.
    • Photo: Julian Onions

      Julian Onions answered on 14 Nov 2014:

      It’s a very difficult area to study, because we are looking right into the centre of the galaxy. On the way in we have to look through a lot of bright stars, also lots of gas clouds and dust clouds, all of which block our view.
      So therefore we tend to use telescopes in the infra red region of the spectrum to look in that direction, as they can see through a lot of the murkyness.
      What we see when looking is a VERY massive object, around which stars are orbiting very fast, and the only thing we know that can be that heavy and that small is a very large black hole.

      You can see them going around the hidden object in this fascinating video

    • Photo: Helen Johnson

      Helen Johnson answered on 16 Nov 2014:

      We’ve also seen X-ray and radio emission from this central region, which confirms our theory of there being a supermassive black hole there. Here’s an image taken at X-ray wavelengths –
      We think this central black hole is about 4 million times more massive than the Sun!

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