Spiral galaxy facts for kids
A spiral galaxy is a type of galaxy that looks like a flat, spinning disk. It has a bright center and arms that curve outwards, like a pinwheel. These amazing cosmic islands are made up of billions of stars, along with gas, dust, and a mysterious substance called dark matter. Right at the very middle of a spiral galaxy, there's usually a giant supermassive black hole.
For a long time, people thought galaxies were just fuzzy clouds called nebulae. It was Edwin Hubble who first described spiral nebulae in his 1936 book, The Realm of the Nebulae. Now we know they are huge groups of stars, and we call them galaxies because of their unique spiral shape.
A barred spiral galaxy is a very common type of spiral galaxy. It has a straight bar of stars across its center, from which the spiral arms extend. There are also other kinds of spiral galaxies:
- Grand-design spiral galaxies have two clear, well-shaped arms.
- Multiple-arm spiral galaxies have more than two arms.
- Flocculent spiral galaxies have arms that are hard to see because they are choppy and not clearly defined.
About 60% of the galaxies close to us in the universe are either spiral or irregular (meaning they don't have a clear shape). You'll usually find them in areas where galaxies are not packed too closely together. They are rare in the very crowded centers of galaxy clusters.
What Are Spiral Arms?
Spiral arms are bright areas within spiral galaxies. They stretch out from the galaxy's central part. These arms are full of dust, gas, and groups of young, hot, and very big stars called star clusters. Because these young stars are so bright, the arms shine more brightly than the galaxy's center. Some spiral galaxies even have yellow, "fossil" arms made of older stars.
Our Home: The Milky Way Galaxy
Our own galaxy, the Milky Way, was discovered to be a spiral galaxy in the early 1900s. Later, in the 1990s, scientists found out it's actually a barred spiral galaxy! It's tricky to see the bar from our spot within the Milky Way's disk. The best proof for its existence came from a study of stars in the galaxy's center, done by the Spitzer Space Telescope.
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
