Hubble Images Nucleus of Andromeda Galaxy

Credit: NASA, ESA, and T. Lauer (National Optical Astronomy Observatory)

The Hubble space telescope has taken a picture of the Nucleus of Andromeda Galaxy. Also known as spiral galaxy M31 Andromeda has a supermassive central black hole of about 100,000,000 solar masses. The black hole's event horizon is not visible in what is the sharpest visible-light picture of the nucleus of a galaxy other than our own, but it can be found near the middle of the small cluster of blue stars at the image's center. This cluster is surrounded by a larger ring of mainly red stars that give the apparents of a double nucleus.

Based on the standard model of stellar evolution  and nebula theory of star formation these blue stars near the central black hole can not be be any older than 200,000,000, years meaning that they had to originate the black hole since this makes them too short-lived to have migrate from elsewhere. This has astronomers puzzled over how such young stars could survive let alone form under the black hole's gravitational pull. Similar stars are also closely found close to the Milky Way's central black hole suggesting this could be common in spiral galaxies.