Clusters of galaxies are formed by the merger of smaller units of matter, such as galaxy groups or individual galaxies. The infalling material (which contains galaxies, gas and dark matter) gains kinetic energy as it falls into the cluster's gravitational potential well. The infalling gas collides with gas already in the cluster and is shock heated to between 107 and 108 K depending on the size of the cluster. This very hot gas emits X-rays by thermal bremsstrahlung emission, and line emission from metals (in astronomy, 'metals' often means all elements except hydrogen and helium). The galaxies and dark matter are collisionless and quickly become virialised, orbiting in the cluster potential well.
The GOES 14 spacecraft carries a Solar X-ray Imager to monitor the Sun's X-rays for the early detection of solar flares, coronal mass ejections (CME), and other phenomena that impact the geospace environment.
GOES 14 was launched into orbit on June 27, 2009 at 22:51 GMT from Space Launch Complex 37B at the Cape Canaveral Air Force Station. GOES 14 is the most recent satellite to be launched with X-ray detection capability. The importance of X-ray astronomy is exemplified in the use of an X-ray imager such as the one on GOES 14 for the early detection of solar flares, CMEs and other X-ray generating phenomena that impact the Earth.
The Crab Nebula is a remnant of an exploded star. This is the Crab Nebula in various energy bands, including a hard X-ray image from the HEFT data taken during its 2005 observation run. Each image is 6′ wide.
...that the first extrasolar X-ray source may have been the diffuse X-ray background. The first Aerobee 150 sounding rocket flight that apparently discovered Scorpius X-1 may have occurred on June 12th or 19th, 1962, and may not have been able to resolve Scorpius X-1 from the Galactic Center as the X-ray detector on board was designed to detect X-rays from the Moon.
...that as the constellation Serpens is actually divided into Serpens Cauda and Serpens Caput, Serpens X-1 is in Serpens Cauda and Serpens Caput was perhaps ignored.
...that some X-ray sources although initially detected as the first X-ray source in a respective constellation may not have received the designation X-1 as they are diffuse sources, contain several X-ray sources within the celestial object, or occupy area in two constellations. The Large Magellanic Cloud (LMC) is in Dorado and Mensa and contains many X-ray sources. Although established as the first X-ray source in Dorado, the LMC was never designated as Dorado X-1. It was first detected on October 29, 1968.
...that an occasional source such as Triangulum Australe X-1 was designated as the X-1 yet another source in the same constellation had been detected earlier and confirmed prior to its detection. The same may have happened to Orion X-1.
...that Carina X-1 (Car X-1) may have been a misprint for Cir X-1.