The
Whirlpool Galaxy, also known as
Messier 51a,
M51a, and
NGC 5194, is an
interactinggrand-designspiral galaxy with a
Seyfert 2active galactic nucleus. It lies in the
constellationCanes Venatici, and was the first galaxy to be classified as a spiral galaxy. Its distance is 31 million
light-years away from Earth.The galaxy and its companion,
NGC 5195,
[ are easily observed by
amateur astronomers, and the two galaxies may be seen with
binoculars.The Whirlpool Galaxy has been extensively observed by professional astronomers, who study it to understand galaxy structure (particularly structure associated with the
spiral arms) and galaxy interactions.
What later became known as the Whirlpool Galaxy was discovered on October 13, 1773, by
Charles Messier while hunting for objects that could confuse comet hunters, and was designated in
Messier's catalogue as M51. Its companion galaxy,
NGC 5195, was discovered in 1781 by
Pierre Méchain, although it was not known whether it was interacting or merely another galaxy passing at a distance. In 1845,
William Parsons, 3rd Earl of Rosse, employing a 72-inch (1.8 m)
reflecting telescope at
Birr Castle, Ireland, found that the Whirlpool possessed a
spiral structure, the first "nebula" to be known to have one.These "
spiral nebulae" were not recognized as galaxies until
Edwin Hubble was able to observe
Cepheid variables in some of these spiral nebulae, which provided evidence that they were so far away that they must be entirely separate galaxies.
Source: Wikipedia
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