Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2000 September 20
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Gangly Spiral Galaxy NGC 3184
Credit: Al Kelly (JSCAS/NASA) & Arne Henden (Flagstaff/USNO)

Explanation: NGC 3184 is a large spiral galaxy with a small nucleus and long sprawling spiral arms. Although NGC 3184 contains hundreds of billions of stars, the blue colour of its spiral arms comes mostly from relatively few bright young blue stars. The galaxy is not empty of matter between these spiral arms -- the bright stars that highlight the arms were created in huge density waves that circle the centre. Visible with a small telescope towards the constellation of Ursa Major, light takes about 25 million years to reach us from NGC 3184, and about 50,000 years just to cross it. NGC 3184 (Hubble type Sbc) is notable for its high abundance of heavy elements and a supernova that has occurred there recently.

Tomorrow's picture: XZ Gas Bubble

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
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& Michigan Tech. U.