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Stellar astronomy Reference Libraries

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Stellar Astrophysics
2014-01-12 00:00:00

The prominent feature that allows for the existence of life on Earth is the Sun. Radiation from our closest star provides heat and energy to our planet, driving biological processes and providing the necessary conditions for liquid water to naturally exist. But our Sun is only but one star in this vast Universe. And as it turns out, most stars are quite different than the one that...

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...

Stellar Evolution
2004-10-19 04:45:42

Stellar Evolution -- Stellar evolution is the process of formation, life, and death of stars. It is one of the major topics of cosmogony. Star Birth and Life A star starts out as an enormous cloud of gas and dust many light-years across. Star formation begins when the cloud begins to condense under its own gravity. The processes that initiate this contraction are not fully understood....

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

Star Formation -- Star formation is the process by which gas in molecular clouds gets transformed into stars. In the current paradigm of star formation, cores of molecular clouds (regions of specially high density) became gravitationally unstable, and start to concentrate. Part of the gravitational energy lost in the process is radiated in the infrared, another part increases the...

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

Star Designation -- The International Astronomical Union (IAU) is the internationally recognised authority for assigning designations to stars (and other celestial bodies). Many of the star names in use today were inherited from the time before the IAU existed. Other names, mainly for variable stars (including novae and supernovae), are being added all the time. Most stars, however,...

Star
2004-10-19 04:45:42

Star -- A star is a self-gravitating sphere of plasma in hydrostatic equilibrium that generates energy in its interior through the process of nuclear fusion. Energy from this process radiates into space as electromagnetic radiation and neutrinos. Star formation and evolution As learned by star formation astronomers, stars are born in molecular clouds, regions of higher density of...

Solar Nebula
2004-10-19 04:45:42

Solar Nebula -- In astronomy, the solar nebula is the gaseous cloud from which, in the so-called nebular hypothesis of the origin of the solar system, the Sun and planets formed by condensation. In 1755 the German philosopher Immanuel Kant suggested that a nebula in slow rotation, gradually pulled together by its own gravitational force and flattened into a spinning disk, gave birth to the...

Photosphere
2004-10-19 04:45:42

Photosphere -- The photosphere of an astronomical object is the region at which the optical depth becomes one. In other words, the photosphere is the place where an object stops being transparent. It is typically used to describe the Sun or another star. Because stars are large balls of gas, they have no solid surface. However, there is a depth at which the gas stops being transparent to...

Nova
2004-10-19 04:45:42

Nova -- A nova is an enormous nuclear explosion caused by the accretion of hydrogen onto the surface of a white dwarf star. When a white dwarf has a close companion star, the companion will often begin to have its outer atmosphere drawn away from it by the white dwarf's gravity as the companion star ages and expands into a red giant. The gases so captured consist primarily of hydrogen...

Molecular Cloud
2004-10-19 04:45:41

Molecular Cloud -- Molecular clouds are interstellar nebulae that have a density and size sufficient to permit the formation of H2, molecular hydrogen. However, this molecule is difficult to detect, and the molecule most used to trace the H2 is CO (carbon monoxide). The ratio between CO luminosity and H2 mass is roughly constant, although there are reasons to doubt this assumption in...

Word of the Day
Cthulhu
  • A gigantic fictional humanoid alien god being described with a head resembling an octopus and dragon wings and claws, around whom an insane cult developed.
  • Pertaining to the mythos of Cthulhu and additional otherworldly beings created by H. P. Lovecraft or inspired by his writings and imitators.
This word was invented in 1926 by H.P. Lovecraft for his short story, 'The Call of Cthulhu.' 'Cthulhu' may be based on the word 'chthonic,' which in Greek mythology refers to the underworld.
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