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
Wikipedia.
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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 ...
Heart of a galaxy emits gamma rays
Oct 02, 2009 |
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(PhysOrg.com) -- Quite a few distant galaxies turn out to be cosmic delivery rooms. Large numbers of massive stars are born in the hearts of these starburst galaxies, and later explode as supernovae. In the ...
Stripped down: Hubble highlights two galaxies that are losing it
Sep 30, 2009 |
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(PhysOrg.com) -- Ram pressure is the drag force that results when something moves through a fluid -- much like the wind you feel in your face when bicycling, even on a still day -- and occurs in this context ...
Astronomers unveil an amazing, interactive, 360-degree panoramic view of the entire night sky
Sep 14, 2009 |
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(PhysOrg.com) -- The first of three images of ESO's GigaGalaxy Zoom project — a new magnificent 800-million-pixel panorama of the entire sky as seen from ESO's observing sites in Chile — has just been released ...
Is the Milky Way doomed to be destroyed by galactic bombardment? Probably not
Aug 31, 2009 |
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(PhysOrg.com) -- As scientists attempt to learn more about how galaxies evolve, an open question has been whether collisions with our dwarf galactic neighbors will one day tear apart the disk of the Milky ...
Herschel's daring test: A glimpse of things to come
Jun 19, 2009 |
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Herschel opened its 'eyes' on 14 June and the Photoconductor Array Camera and Spectrometer obtained images of M51, 'the whirlpool galaxy' for a first test observation. Scientists obtained images in three colours ...
Why Are Galaxies So Smooth?
May 01, 2009 |
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(PhysOrg.com) -- Using NASA's Spitzer Space Telescope, an international team of astronomers has discovered streams of young stars flowing from their natal cocoons in distant galaxies. These distant rivers ...
A 3-D view of remote galaxies
Mar 10, 2009 |
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For decades, distant galaxies that emitted their light six billion years ago were no more than small specks of light on the sky. With the launch of the Hubble Space Telescope in the early 1990s, astronomers ...
NGC 4945: The Milky Way's not-so-distant Cousin
Sep 02, 2009 |
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(PhysOrg.com) -- ESO has released a striking new image of a nearby galaxy that many astronomers think closely resembles our own Milky Way. Though the galaxy is seen edge-on, observations of NGC 4945 suggest ...
Moonship Photographed by Backyard Astronomers
Space & Earth / Space Exploration
Jul 10, 2009 |
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On June 29th, neighbors of Paul Mortfield in Ontario, Canada, heard "cheers of excitement" coming from the astronomer's house. What caused the commotion?
A Galaxy Collision in Action
Jul 09, 2009 |
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This beautiful image gives a new look at Stephan's Quintet, a compact group of galaxies discovered about 130 years ago and located about 280 million light years from Earth. The curved, light blue ridge running ...
Stars forced to relocate near the Southern Fish
Mar 03, 2009 |
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About 100 million light-years away, in the constellation of Piscis Austrinus (the Southern Fish), three galaxies are playing a game of gravitational give-and-take that might ultimately lead to their merger ...
Web users to write ‘Hitchhiker’s Guide to the Galaxies’
Space & Earth / Space Exploration
Feb 17, 2009 |
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(PhysOrg.com) -- Today saw the launch of Galaxy Zoo 2, a website that invites members of the public to help create a detailed guide to some of the Universe's most fascinating objects. The online project is ...
Black hole outflows from Centaurus A detected with APEX
Jan 28, 2009 |
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(PhysOrg.com) -- Astronomers have a new insight into the active galaxy Centaurus A (NGC 5128), as the jets and lobes emanating from the central black hole have been imaged at submillimetre wavelengths for ...
Submillimeter Eagle Eyes on Mauna Kea
Space & Earth / Space Exploration
Nov 20, 2008 |
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(PhysOrg.com) -- Three observatories on Mauna Kea have come together to form the world's most powerful facility for detailed submillimeter imaging. An exploratory project, the Extended Submillimeter Array ...
