Star Reference Libraries

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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,...

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...

Red Dwarf
2004-10-19 04:45:42

Red Dwarf -- A red dwarf is a small star on the main sequence, either late K or M spectral type. They have a diameter and mass of less than one-third that of the Sun (down to 0.08 solar masses, which are Brown dwarves) and a surface temperature of less than 3,500 K. They emit little light, sometimes as little as 1/10,000th that of the sun. Due to the slow rate at which they burn...

2004-10-19 04:45:42

Pulsar -- A pulsar, which originally stood for pulsating radio source, is a rapidly rotating neutron star, whose electromagnetic radiation is observed in regularly spaced interval, or pulses. Pulsars are closely related to magnetars, the main difference being the strenght of the object's magnetic field. History Pulsars were discovered by Jocelyn Bell and Antony Hewish in 1967 while...

Open Cluster
2004-10-19 04:45:42

Open Cluster -- An open cluster is a group of star formed from a molecular cloud, the illuminated parts of which we see as one or more nebulae. They are also called galactic clusters since they exist within the galaxy. All the stars in an open cluster have more or less the same age and the same chemical composition, so any difference between them is solely due to their mass. Most open...

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...

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...

Double Star
2004-10-19 04:45:41

Double Star -- When two stars are so nearly in the same direction as seen from Earth that they appear to be a single star to the naked eye but may be separated by the use of telescopes, they are referred to as a double star. There are two different kinds of double star. In the case where two stars are only apparently close to each other, but which are in fact separated by a great distance...

Word of the Day
  • The call or cry of a bird or other animal to its mate or its young.
'Call-note' is newer than 'bird-call,' which originally referred to 'an instrument for imitating the note of birds' but now also refers to 'the song or cry of a bird.'