Spiral galaxy facts for kids
A spiral galaxy is a kind of galaxy that looks like a flat, slowly rotating disk with a bulge in the centre, and spiral patterns extending outward from the bulge. It contains stars, gas, dust, dark matter and a supermassive black hole at its centre.
Galaxies were long thought to be nebulas. The spiral nebula as a type was first described by Edwin Hubble in his 1936 work The Realm of the Nebulae. They are now listed as galaxies, and are named after their shape.
The barred spiral galaxy is an important and common type of spiral galaxy. There are three other kinds of spiral galaxies. Grand-design spiral galaxies have two well-shaped and well-defined arms. Multiple-arm spiral galaxies have more arms. In flocculent spiral galaxies, it is hard to see the arms at all, as they are choppy and are ill-defined.
About 60% of galaxies in the universe near us (the 'local universe') are spiral and irregular galaxies. They are mostly found in low-density parts of the universe, and are rare in the centers of galaxy clusters.
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Spiral arms
Spiral arms are regions in spiral galaxies. They often contain dust,gas and star clusters of young ,hot and massive stars. They extend from the central bulge area of spiral and barred spiral galaxies. The young, hot and massive stars are why the arms are brighter than the center of the galaxy. Some spiral galaxies have yellow, 'fossil' arms of older stars.
Milky Way
Our own Milky Way was found to be a spiral galaxy in the early 20th century. In the 1990s it was found to be a barred spiral galaxy. The bar is difficult to see from our position in the Galactic disk. The most convincing evidence for its existence comes from a survey, performed by the Spitzer Space Telescope, of stars in the Galactic center.
Images for kids
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Barred spiral galaxy UGC 12158.
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Spiral galaxy NGC 1589
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Spiral galaxy NGC 2008
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Spiral galaxy NGC 1345
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NGC 428 is a barred spiral galaxy, located approximately 48 million light-years away from Earth in the constellation of Cetus.
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Spiral galaxy NGC 6384 taken by Hubble Space Telescope.
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The spiral galaxy NGC 1084, home of five supernovae.
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The bright galaxy NGC 3810 demonstrates classical spiral structure in this very detailed image from Hubble. Credit: ESA/Hubble and NASA.
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See also
In Spanish: Galaxia espiral para niños
