Star types Reference Libraries

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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...

Hertzsprung-Russell Diagram
2004-10-19 04:45:43

Hertzsprung-Russell Diagram -- In stellar astronomy, the Hertzsprung-Russell diagram (H-R diagram) shows the relation between the absolute magnitude and the spectral types of stars. It was invented around 1910 by Ejnar Hertzsprung and Henry Norris Russell. There are two equivalent forms. One is the observer's form which plots the color of the star on one axis and the absolute magnitude on...

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

X-ray Pulsar -- This dramatic artist's vision shows a city-sized neutron star centered in a disk of hot plasma drawn from its enfeebled red companion star. Ravenously accreting material from the disk, the neutron star spins faster and faster emitting powerful particle beams and pulses of X-rays as it rotates 400 times a second. Could such a bizarre and inhospitable star system really exist...

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...

White Dwarf
2004-10-19 04:45:43

White Dwarf -- A white dwarf is a a star supported by electron degeneracy. A star like our Sun will become a white dwarf when it has exhausted its nuclear fuel. Near the end of its nuclear burning stage, such a star goes through a red giant phase and then expels most of its outer material (creating a planetary nebula) until only the hot (T > 100,000 K) core remains, which then settles...

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...

Triple Star
2004-10-19 04:45:42

Triple Star -- A triple star system consists of three gravitationally bound stars. The stars are in orbits around a common center of mass, usually so that two of the stars form a close binary star and the third is further away. This configuration is often called a hierarchical triple star. Multiple stars containing more than three stars can usually be decomposed to binaries and...

T Tauri
2004-10-19 04:45:42

T Tauri -- T Tauri stars are a class of stars thought to represent extremely young pre-main sequence stars, in an early stage of life. They are seen near many molecular clouds in our galaxy. The first ones were found in 1945, identified by their optical variability and strong chromospheric lines. T Tauri stars have masses and temperatures similar to the Sun, but are significantly...

2004-10-19 04:45:42

Supernova -- A supernova is a star that increases its brightness drastically within a matter of days, making it appear as if a "new" star was born (hence "nova"). The "super" prefix distinguishes it from a mere nova, which also involves a star increasing in brightness, though to a lesser extent and through a much different mechanism. Astronomers have classified supernovae in several...

Word of the Day
  • A poem in which the author retracts something said in an earlier poem.
The word 'palinode' comes from Greek roots meaning 'again' and 'song'.