Spiral galaxy
hideA spiral galaxy is a galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the Nebulae” and, as such, forms part of the Hubble sequence. Spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge. These are surrounded by a much fainter halo of stars, many of which reside in globular clusters.
Spiral galaxies are named for the (usually two-armed) spiral structures that extend from the center into the disk. The spiral arms are sites of ongoing star formation and are brighter than the surrounding disk because of the young, hot OB stars that inhabit them. Roughly half of all spirals are observed to have an additional component in the form of a bar-like structure, extending from the central bulge, at the ends of which the spiral arms begin. Our own Milky Way has been recently (in the 1990s) been confirmed to be a barred spiral, although the bar itself is difficult to observe from our position within the Galactic disk. The most convincing evidence for its existence comes from a recent survey, performed by the Spitzer Space Telescope, of stars in the Galactic center.
Together with irregulars, spiral galaxies make up approximately 60% of galaxies in the local Universe. They are mostly found in low-density regions and are rare in the centers of galaxy clusters.
For more information about Spiral galaxy, read the full article at
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News tagged with spiral galaxy
NGC 4710 galaxy: Baffling boxy bulge (w/ Video)
Nov 18, 2009 |
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(PhysOrg.com) -- Just as many people are surprised to find themselves packing on unexplained weight around the middle, astronomers find the evolution of bulges in the centres of spiral galaxies puzzling. A ...
University of Utah celebrates telescope's 'first light'
Nov 04, 2009 |
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(PhysOrg.com) -- The University of Utah will celebrate the initial observations or "first light" of its new $860,000 research telescope in southwest Utah during a Wednesday, Nov. 11 symposium and reception ...
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Hubble Image Showcases Star Birth in M83, the Southern Pinwheel
Nov 05, 2009 |
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(PhysOrg.com) -- The spectacular new camera installed on NASA's Hubble Space Telescope during Servicing Mission 4 in May has delivered the most detailed view of star birth in the graceful, curving arms of ...
'Cosmic fruit machine' matches collisions
Nov 24, 2009 |
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(PhysOrg.com) -- A new website will give everyone the chance to contribute to science by playing a 'cosmic fruit machine' and compare images of colliding galaxies with millions of simulated images of galactic ...
Maps Unveil the Source of Starburst Galaxy's Winds
Nov 18, 2009 |
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(PhysOrg.com) -- A research group at Kyoto University has discovered that shocks are the primary energy sources that excite the galactic wind region of starburst galaxy NGC 253. Their images of the center ...
Herschel takes a peek at the ingredients of the galaxies
Nov 27, 2009 |
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(PhysOrg.com) -- The European Space Agency has today released spectacular new observations from the Herschel Space Observatory, including the UK-led SPIRE instrument. Spectrometers on board all three Hershel ...
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