Celestial hemisphere:  Northern  ·  Constellation: Canes Venatici (CVn)  ·  Contains:  IC 4263  ·  M 51  ·  NGC 5169  ·  NGC 5194  ·  NGC 5195  ·  NGC 5198  ·  Whirlpool galaxy
M51 Whirlpool Galaxy, Dick Krause
M51 Whirlpool Galaxy
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M51 Whirlpool Galaxy

M51 Whirlpool Galaxy, Dick Krause
M51 Whirlpool Galaxy
Powered byPixInsight

M51 Whirlpool Galaxy

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Description

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. It was, however, not until 1845 that William Parsons, 3rd Earl of Rosse, employing a 72-inch (1.8 m) reflecting telescope at Birr Castle, Ireland, found 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.

The advent of radio astronomy and subsequent radio images of M51 unequivocally demonstrated that the Whirlpool and its companion galaxy are indeed interacting. Sometimes the designation M51 is used to refer to the pair of galaxies, in which case the individual galaxies may be referred to as M51A (NGC 5194) and M51B (NGC 5195).

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M51 Whirlpool Galaxy, Dick Krause