The Universe is very large and possibly infinite in volume; the observable matter is spread over a space at least 93 billion
light years across.
[14] For comparison, the diameter of a typical
galaxy is only 30,000 light-years, and the typical distance between two neighboring galaxies is only 3 million
light-years.
[15] As an example, our
Milky Way Galaxy is roughly 100,000 light years in diameter,
[16] and our nearest sister galaxy, the
Andromeda Galaxy, is located roughly 2.5 million light years away.
[17] There are probably more than 100 billion (1011)
galaxies in the
observable universe.
[18] Typical galaxies range from
dwarfs with as few as ten million
[19] (107)
stars up to giants with one
trillion[20] (1012) stars, all orbiting the galaxy's center of mass. Thus, a very rough estimate from these numbers would suggest there are around one
sextillion (1021) stars in the observable universe; though a 2003 study by Australian National University astronomers resulted in a figure of 70 sextillion (7 x 1022)
[21].