One of the farthest stars that I know about is called 'V12' or Variable 12, in the galaxy NGC 4203. This galaxy is located 3.2 million parsecs away or 10.4 million light years away and is one of the brightest individual stars in that galaxy. Out of the billions of stars in a typical large galaxy, only a handful are the most individually luminous. These are the individual stars that can be seen over intergalactic distances.
The nearby Andromeda galaxy can be photographed to reveal individual stars which are mostly of the 'giant' class meaning that their luminosities are about 10 to 100 times that of the Sun. A star like our own Sun is not powerful enough to be seen this far. The star V12 is about 10 million times brighter that our own Sun and stars like it can be seen in galaxies that are millions of light years from the Milky Way.
The Hubble Space Telescope is such a powerful telescope, that it can see individual stars in the galaxy Messier 100 which is as far away as the so-called 'Virgo Cluster' of galaxies. Just like stars, galaxies which themselves contain billions of stars, can also be found in groups of 10, 100 or even 10,000 other galaxies; swarming through intergalactic space like some enormous hive of bees! By measuring how a few dozen special 'Cepheid variable' stars change their brightness, astronomers can tell just how powerful these stars are compared to the Sun, and use this to figure out very accurately just how far the galaxy they are located in is from the Milky Way.
Copyright 1997 Dr. Sten Odenwald
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