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.

January 25, 1997

M51: The Whirlpool Galaxy
Credit: W. Keel (U. Alabama), 1.1-metre Hall Telescope, Lowell Observatory

Explanation: The Whirlpool Galaxy is a classic spiral galaxy. At only 15 million light years distant, M51, also catalogued as NGC 5194, is one of the brighter and more picturesque galaxies on the sky. The smaller galaxy appearing here above and to the right is also well behind M51, as can be inferred by the dust in M51's spiral arm blocking light from this smaller galaxy. Astronomers speculate that M51's spiral structure is primarily due to it's gravitational interaction with this smaller galaxy.

Tomorrow's picture: Aurora and Orion

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
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