The
Whirlpool Galaxy, also known as
Messier 51a (
M51a) or
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. It is 7.22 megaparsecs (23.5 million light-years) away and 23.58 kiloparsecs (76,900 ly) in diameter.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 and its pair with NGC 5195 to understand galaxy structure (particularly structure associated with the
spiral arms) and galaxy interactions. Its pair with
NGC 5195 is among the most famous and relatively close interacting systems, and thus is a favorite subject of galaxy interaction models.Discovery
Sketch of M51 by
Lord Rosse in 1845
William Parsons, 3rd Earl of Rosse[color=var(--lighterGrey)], employing a 72-inch (1.8 m) [/color]
reflecting telescope[color=var(--lighterGrey)] at [/color]
Birr Castle[color=var(--lighterGrey)], Ireland, found that the Whirlpool possessed a [/color]
spiral structure[color=var(--lighterGrey)], the first "nebula" to be known to have one.[/color][color=var(--lighterGrey)] These "[/color]
spiral nebulae[color=var(--lighterGrey)]" were not recognized as galaxies until [/color]
Edwin Hubble[color=var(--lighterGrey)] was able to observe [/color]
Cepheid variables[color=var(--lighterGrey)] in some of these spiral nebulae, which provided evidence that they were so far away that they must be entirely separate galaxies. The Whirlpool Galaxy was discovered on October 13, 1773, by [/color]
Charles Messier[color=var(--lighterGrey)] while searching for objects that might confuse comet hunters. It was later cataloged as M51 in [/color]
Messier's[color=var(--lighterGrey)] list of astronomical objects.[/color]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).Visual appearance
The image of the Whirlpool Galaxy in visible light (left) and infrared light (right)Deep in the constellation
Canes Venatici, M51 is often found by finding the easternmost star of the
Big Dipper,
Alkaid, and going 3.5° southwest. Its declination is, rounded, +47°, making it
circumpolar (never setting) for observers above the
43rd parallel north;
[a] it reaches a high altitude throughout this hemisphere making it an accessible object from the early hours in November through to the end of May, after which observation is more coincidental in modest latitudes with the risen sun (due to the Sun approaching to and receding from its
right ascension, specifically figuring in
Gemini, just to the north).M51 is visible through
binoculars under dark sky conditions, and it can be resolved in detail with modern amateur telescopes. When seen through a 100 mm telescope the basic outlines of M51 (limited to 5×6') and its companion are visible. Under dark skies, and with a moderate eyepiece through a 150 mm telescope, M51's intrinsic spiral structure can be detected. With larger (>300 mm) instruments under dark sky conditions, the various spiral bands are apparent with
HII regions visible, and M51 can be seen to be attached to
M51B.As is usual for galaxies, the true extent of its structure can only be gathered from inspecting photographs; long exposures reveal a large nebula extending beyond the visible circular appearance. In 1984, thanks to the high-speed detector—the so-called image-photon-counting-system (IPCS)—developed jointly by the CNRS Laboratoire d'Astronomie Spatiald (L.A.S.-CNRS) and the Observatoire de Haute Provence (O.H.P.) along with the particularly nice visibility offered by the Canada-France-Hawaii-Telescope (C.F.H.T.) 3.60m Cassegrain focus on the summit of Mauna Kea in Hawaii, Hua et al. detected the double component of the very nucleus of the Whirlpool Galaxy.In January 2005 the
Hubble Heritage Project constructed a 11,477 × 7,965-pixel composite image (shown in the infobox above) of M51 using Hubble's
ACS instrument. The image highlights the galaxy's spiral arms, and shows detail into some of the structures inside the arms.
Source Wilkpedia
Sketch of M51 by Lord Rosse in 1845
The image of the Whirlpool Galaxy in visible light (left) and infrared light (right)Deep in the constellation Canes Venatici, M51 is often found by finding the easternmost star of the Big Dipper, Alkaid, and going 3.5° southwest. Its declination is, rounded, +47°, making it circumpolar (never setting) for observers above the 43rd parallel north;[a] it reaches a high altitude throughout this hemisphere making it an accessible object from the early hours in November through to the end of May, after which observation is more coincidental in modest latitudes with the risen sun (due to the Sun approaching to and receding from its right ascension, specifically figuring in Gemini, just to the north).M51 is visible through binoculars under dark sky conditions, and it can be resolved in detail with modern amateur telescopes. When seen through a 100 mm telescope the basic outlines of M51 (limited to 5×6') and its companion are visible. Under dark skies, and with a moderate eyepiece through a 150 mm telescope, M51's intrinsic spiral structure can be detected. With larger (>300 mm) instruments under dark sky conditions, the various spiral bands are apparent with HII regions visible, and M51 can be seen to be attached to M51B.As is usual for galaxies, the true extent of its structure can only be gathered from inspecting photographs; long exposures reveal a large nebula extending beyond the visible circular appearance. In 1984, thanks to the high-speed detector—the so-called image-photon-counting-system (IPCS)—developed jointly by the CNRS Laboratoire d'Astronomie Spatiald (L.A.S.-CNRS) and the Observatoire de Haute Provence (O.H.P.) along with the particularly nice visibility offered by the Canada-France-Hawaii-Telescope (C.F.H.T.) 3.60m Cassegrain focus on the summit of Mauna Kea in Hawaii, Hua et al. detected the double component of the very nucleus of the Whirlpool Galaxy.In January 2005 the Hubble Heritage Project constructed a 11,477 × 7,965-pixel composite image (shown in the infobox above) of M51 using Hubble's ACS instrument. The image highlights the galaxy's spiral arms, and shows detail into some of the structures inside the arms.
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