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.

December 18, 1995

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

Explanation: The Whirlpool Galaxy is frequently given as an example of a galaxy with classic spiral design. At only 15 million light years distant, M51, also catalogued as NGC 5194, is also 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: Albert Einstein: 1879 - 1955

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