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X-ray Reference Libraries

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Abell 2142
2010-09-07 17:13:57

Abell 2142, also called A2142 and located in the constellation Corona Borealis, is an X-ray luminous galaxy cluster. Its creation is due to the merger between two galaxy clusters. It is one of the largest objects in the universe and is six million light years across. It holds hundreds of galaxies and enough gas to make a thousand more. The pressure fronts in the system have been traced in...

X-Ray Astronomy
2004-10-19 04:45:44

X-Ray Astronomy -- Although the more energetic X-rays (E > 30 keV) can penetrate the air at least for distances of a few meters (they would never have been detected and medical X-ray machines would not work if this was not the case) the Earth's atmosphere is thick enough that virtually none are able to penetrate from outer space all the way to the Earth's surface. X-rays in the 0.5 - 5 keV...

X-ray Burster
2004-10-19 04:45:43

X-ray Burster -- X-ray bursters are a class of binary stars which are luminous in X-rays. They contain a neutron star and a low-mass companion star. The companion fills its Roche lobe and therefore the neutron star is accreting matter from it. The inflowing gas forms an accretion disk around the neutron star. Sometimes X-ray bursters show a sudden increase in their X-ray luminosity, called...

X-ray Binaries
2004-10-19 04:45:43

X-ray Binaries -- X-ray binaries are a class of binary stars that are very luminous in X-rays. The X-rays are produced by matter falling from one component (usually a relatively normal star) to the other component, which is a neutron star or a black hole. The infalling matter releases gravitational potential energy, up to several tens of per cent of its rest mass as X-rays. (Hydrogen...

Variable Star
2004-10-19 04:45:43

Variable Star -- Most stars are of nearly constant luminosity. Our own Sun is a good example which goes through practically no measurable variation in brightness. There are, however, stars which do vary in brightness, called variable stars. They fall into two main groups: Intrinsic variables These are stars which have intrinsic variations in brightness, that is the star itself gets...

Microquasar
2004-10-19 04:45:41

Microquasar -- Microquasars are smaller cousins of quasars. They are named after quasars, as they have some common characteristics: strong and variable radio emission often seen as radio jets, and an accretion disk surrounding a black hole. In quasars, the black hole is supermassive (millions of solar masses) as in microquasars, the black hole mass is a few solar masses. In microquasars,...

Magnetar
2004-10-19 04:45:41

Magnetar -- A magnetar is a neutron star with a strong magnetic field. The theory around these objects was formulated by Robert Duncan and Christopher Thompson. When in a supernova a star collapses to a neutron star, its magnetic field increases dramatically in strength. Duncan and Thompson calculated that the magnetic field of a neutron star, normally an already enormous 1012 tesla...

Globular Cluster
2004-10-19 04:45:41

Globular Cluster -- A globular cluster is a cluster of stars that is spherical in shape and extremely dense towards its core. Globular clusters are usually composed of hundreds of thousands of old stars, similar to the bulge of a spiral galaxy but confined to a volume of only a few cubic parsecs. Some globular clusters (like Omega Centauri in our Milky Way, and G1 in M31) are truly massive...

Electromagnetic Spectrum
2004-10-19 04:45:41

Electromagnetic Spectrum -- The electromagnetic spectrum describes the various types of electromagnetic radiation based on their wavelengths. Radio, representing wavelengths from a few feet to well over a mile, is at one end of the spectrum. Gamma ray radiation is at the other end: the wavelength of the harder types is so short, in the subatomic range, that we do not have instruments...

Crab Nebula
2004-10-19 04:45:40

Crab Nebula -- The Crab Nebula (Messier 1, NGC 1952) is the object the which started Charles Messier logging non-cometary objects on his Messier Catalog. It is the expanding cloud of gas thrown off in the explosion that gave rise to the 1054 supernova recorded by Chinese astronomers, now more than 6 light years across (the nebula is currently expanding at 1000 km/sec and the total mass of...

Word of the Day
tourtiere
  • a meat pie that is usually eaten at Christmas in Quebec
The word 'tourtiere' comes from the French tourte, or passenger pigeon.
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