This section is devoted to cosmic X-ray sources or topics that do not fit in any of the other categories in "X-Ray Sources".
Brown Dwarfs - Clouds of collapsing gas and dust that did not contain enough mass to initiate core nuclear fusion. Such objects are then frozen somewhere along their pre- main sequence contraction phase, continuously cooling into compact dark objects. Because of their small size and low temperature, they are extremely difficult to detect observationally.
Gamma Ray Bursts - An outburst that radiates tremendous amounts of energy in a few minutes equal to or greater than a supernova, in the form of gamma rays. Such objects were discovered by accident in the late 1960's by satellites designed to detect gamma rays produced by atomic bomb tests on Earth.