Supermassive black hole powers the Andromeda galaxy
A massive black hole with the mass of 140,000,000 suns(!) has been found at the center of the Andromeda galaxy, surrounding by fast-orbiting, hot, blue stars similar to Sirius, which is the brightest visible star in our own night sky. These blue stars are orbiting so quickly that their speed can only be explained by the existence of a massive black hole. By calculating the speed of their orbit, scientists have determined the mass of what they are orbiting.
It has been suspected that a black hole existed at the center of Andromeda, but other theories have suggested that it was inhabited by dead and dying brown dwarf stars. However, the measurement of the speed of the blue stars’ orbit has laid that theory to rest. The measurements were made using data from a now-defunct spectrometer on the Hubble Space Telescope — which is an unusual use for a spectrometer.
It is suspected that there are 35 other galaxies with supermassive black holes at their centers, though only two have actually been confirmed: our own Milky Way, and M106. It is doubtful whether black holes in the other 35 galaxies will ever be confirmed because they are so far away. (Though personally I believe determinations will be made in the next 50 years, with the rate that technology is progressing.) Andromeda is the closest galaxy to our own, and it is easier to look into than the Milky Way due to its orientation: we are on the outskirts of the Milky Way, and looking towards the center of our galaxy is difficult. Because Andromeda is removed somewhat, studying it is easier.
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