The diameter value above refers to the maximum extent of the galaxy's halo. The brighter central parts are approximately 3° in diameter, corresponding to an actual value of about 120,000 light years.
The most famous of all galaxies is also the most distant object visible to the naked eye, and the nearest major galaxy to the Milky Way. In some ways its spiral structure resembles that of our own Galaxy, but it is about twice as massive.
The distance to the AndromedaGalaxy is immense: some 2,500,000 light years, but nonetheless its vast size and luminosity mean that it is still visible to the naked eye (in fact, it is the most distant object that can been seen without a telescope). Even so, much of the structure in its spiral arms is too faint to be seen, so that it appears smaller than it actually is: if we could see the entire galaxy, it would occupy an area of the sky nearly six times the size of the Moon's disc.
The galaxy is most visible in the northern sky towards the end of autumn and beginning of winter. The constellation of Andromeda is simple to locate: a imaginary line from the Pole Star through the 'W' of Cassiopeia leads directly to it, and the pale form of the AndromedaGalaxy is not hard to find in its central regions.