The Minor Planet Center, located at the Smithsonian Astrophysical Observatory (SAO) in Cambridge, Mass., has announced the recipients of the 2013 Edgar Wilson Award for the discovery of comets by amateurs.
A new study of gamma-ray light from the center of our galaxy makes the strongest case to date that some of this emission may arise from dark matter, an unknown substance making up most of the material universe.
Galaxy clusters are groupings of several to thousands of galaxies. Most galaxies are members of a cluster. In our own case, the Milky Way is a member of the "Local Group," a band of about fifty galaxies whose other large member is the Andromeda galaxy about 2.3 million light-years away.