Galaxy formation and evolution Reference Libraries

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Coma Cluster
2010-09-13 16:56:08

The Coma Cluster (Abell 1656), along with the Leo Cluster, is one of two major clusters compromising the Coma Supercluster. It contains over 1000 identified galaxies. Most of the galaxies in the center of the Coma Cluster are elliptical galaxies including both dwarf and giant. However the center is dominated by NGC 4874 and NGC 4889, two giant elliptical galaxies. The brightest galaxies are...

Abell 520
2010-09-07 17:03:18

The Abell 520 galaxy cluster is an strange structure formed by a major merger. Due to its odd and chaotic nature it has been given the nick-name the Train Wreck Cluster. The Dark Matter within the cluster does not act as expected like it does in other clusters, therefore, Abell 520 creates problems for many of the prevailing theories about Dark Matter. It also disrupts many alternative...

Ring Galaxy
2004-10-19 04:45:42

Ring Galaxy -- A subclass of interacting galaxies, ring galaxies, provides a unique laboratory for studying unusually large bursts of non-nuclear star formation. The rings in these systems are often large (10s of kiloparsecs) and contain what appear to be associations of giant H{\small II} regions. As a basis for future modeling of star forming regions in observed ring galaxies we...

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...

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...

Elliptical Galaxy
2004-10-19 04:45:41

Elliptical Galaxy -- In astronomy, one of the main classes of galaxy in the Hubble classification and characterized by a featureless elliptical profile. Unlike spiral galaxies, elliptical galaxies have very little gas or dust and no stars have recently formed within them. They range greatly in size from giant ellipticals, which are often found at the centres of clusters of galaxies and...

Big Bang
2004-10-19 04:45:41

Big Bang -- The Big Bang theory is the dominant theory in cosmology about the early development and current shape of the universe. According to this theory, the universe expanded rapidly starting 13.7 0.2 billion years ago. Extrapolating the history of the universe backwards using current physical models leads to a gravitational singularity, at which all distances become zero and...

Seyferts Sextet
2004-10-19 04:45:40

Seyfert's Sextet -- Seyfert's Sextet is a group of galaxies in which gravitational forces are exerted between its members. The galaxies are so tightly packed together that gravitational forces are beginning to rip stars from them and distort their shapes. Those same gravitational forces eventually could bring the galaxies together to form one large galaxy. The name of this grouping,...

Milky Way Galaxy
2004-10-19 04:45:40

Milky Way Galaxy -- The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Galaxia (gala, galactos means "milk")) is a hazy band of white light across the night sky formed by billions of stars in the disc of our galaxy. The Milky Way appears brightest in the direction of Sagittarius, where the galactic centre lies. Relative to the celestial equator, the Milky...

Word of the Day
  • A handkerchief.
  • Specifically— The legendary sweat-cloth; the handkerchief of St. Veronica, according to tradition miraculously impressed with the mask of Christ; also, the napkin about Christ's head (Johu xx. 7).
  • In general, any miraculous portrait of Christ.
The word 'sudarium' comes from a Latin word meaning 'a handkerchief'.