Elliptical galaxy in Virgo
Messier 87 is an enormous galaxy, containing about one trillion stars. In the center of the galaxy is a massive black hole. Although no black hole can be seen directly, the effects of this one are clearly visible near the galaxy's nucleus, where a long jet of material expelled from the black hole can be seen (to the right in this image).
An estimate of this galaxy's angular size is given in the table below, but as this image shows, determining the extent of a galaxy like this is difficult and arbitrary. A bright center gradually fades off until it blends with the sky.
Rolling over the image identifies some of the other galaxies in this image.
Image details: Exposure times of 120 minutes luminance, and 40 minutes each of red, green, and blue, taken with an SBIG ST-8300M imager and a 14" Meade LX850 telescope at f/6.