Optical Image of the Andromeda Galaxy
This optical image of the Andromeda Galaxy (M31) shows the beautiful spiral structure of a spiral galaxy. M31 is our nearest neighbor spiral galaxy (outside of the Milky Way), and therefore offers us a view of what the Milky Way might look like if we could travel from our current location in the middle of a Milky Way spiral arm to a point high above our galaxy. The black square in the center shows the size of the nuclear region imaged by Chandra.
(Credit: Dr. M. Garcia, Dr. S. Murray, Palomar Sky Survey)

X-ray/Optical Composite
This composite shows the optical image of M31 with an inset consisting of the Chandra X-ray image of the nucleus. An approximate temperature scale is also shown for the X-ray image. In order to emit X-rays, gas must be very hot: hotter than a million degrees Centigrade. The gas falling into the super massive black hole in the nucleus of M31 is cool only by comparison to the other X-ray emitting stars and black holes nearby: They are typically 20 million degrees!
(Credit: X-ray: NASA/CXC/SAO; Optical: M.Garcia, S.Murray, Palomar Sky Survey)

Chandra X-ray Image with Scale Bar
Scale bar = 5 arcsec
(Credit: NASA/CXC/SAO)