Universe Reference Libraries

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2014-01-12 00:00:00

Image Caption: The Hubble Extreme Deep Field (XDF) was completed in September 2012 and shows the farthest galaxies ever photographed by humans. Each speck of light in the photo is an individual galaxy, some of them as old as 13.2 billion years; the observable universe is estimated to contain more than 200 billion galaxies. Credit: NASA/Wikipedia What is Cosmology? I once commented to an...

2014-01-12 00:00:00

Physics is a natural science involving the study of matter and its motion through space-time, along with related concepts such as energy and force. On a broader scale, it also involves the general analysis of nature, conducted in order to understand how the universe behaves. Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy. Physics was...

Lyra Constellation
2004-10-19 04:45:44

Lyra Constellation -- Lyra (the lyre) is a prominent, although fairly small, northern constellation. It was one of Ptolemy's 48 constellations, and also counts among the modern 88 constellations. Its brightest star is Vega (Alpha Lyrae), which together with Altair (Alpha Aquilae) and Deneb (Alpha Cygni) forms the large asterism known as the Summer Triangle. Beta Lyr is a half separated...

Cygnus Constellation
2004-10-19 04:45:44

Cygnus Constellation -- Cygnus (the swan) is a northern constellation. It was one of Ptolemy's 48 constellations, and is also one of the 88 modern constellations. Because of the pattern of its main stars, it is sometimes called the Northern Cross (in contrast to the Southern Cross). The bird extends over the summer Milky Way, appearing to fly south. Notable features Cygnus contains...

Centaurus Constellation
2004-10-19 04:45:44

Centaurus Constellation -- Centaurus (the centaur) was one of the 48 constellations listed by Ptolemy, and counts also among the 88 modern constellations. A constellation of the southern hemisphere, mentioned by Eudoxus (4th century B.C.) and Aratus (3rd century B.C.), Ptolemy catalogued thirty-seven stars in it. It contains Proxima Centauri, the red dwarf that is the nearest known star...

Large-Scale Structure of the Cosmos
2004-10-19 04:45:44

Large-Scale Structure of the Cosmos -- Stars are organised into galaxies which in turn appear to form clusters and superclusters, separated by voids. Prior to 1989 it was commonly assumed that the superclusters were the largest structures in existence, and that they were distributed more-or-less uniformly throughout the universe in every direction. However, in 1989, Margaret Geller and...

2004-10-19 04:45:44

Cosmology -- area of science that aims at a comprehensive theory of the structure and evolution of the entire physical universe. Modern Cosmological Theories Present models of the universe hold two fundamental premises: the cosmological principle and the dominant role of gravitation. Derived by Hubble, the cosmological principle holds that if a large enough sample of galaxies is...

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...

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...

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

Star Cluster -- Star clusters are physically bound systems of stars. In order of low compactness to high compactness (and in some sense also age) they range from stellar associations to open clusters to globular clusters. Star clusters are held together by the gravitation of their members. Due to both external (encounters with massive objects, influence of the host galaxy) and internal...

Word of the Day
  • A young chicken: also used as a pet name for children.
The word 'chickabiddy' may come from 'chick' plus 'biddy', a name used in calling a hen or chicken.