Misplaced Pages

This is an old revision of this page, as edited by 2.25.45.251 (talk) at 23:44, 28 July 2017 (the IAU is the arbiter of names of astronomical objects. this name has no status and seems to be just someone's personal nickname for it.). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Whirlpool Galaxy
Whirlpool Galaxy (M51A or NGC 5194). The smaller object in the upper right is M51B or NGC 5195. Credit: NASA/ESA
Observation data (J2000 epoch)
Constellation	Canes Venatici
Right ascension	13 29 52.7
Declination	+47° 11′ 43″
Redshift	463 ± 3 km/s
Distance	23.000 Mly (7.1 ± 1.2 Mpc)
Apparent magnitude (V)	8.4
Characteristics
Type	SA(s)bc pec
Size	~60,000ly in diameter
Apparent size (V)	11′.2 × 6′.9
Notable features	Interacting with NGC 5195
Other designations
Question Mark Galaxy, Rosse's Galaxy, M51a, NGC 5194, UGC 8493, PGC 47404, VV 001a, VV 403, Arp 85, GC 3572

The Whirlpool Galaxy, also known as Messier 51a, M51a, and NGC 5194, is an interacting grand-design spiral galaxy with a Seyfert 2 active galactic nucleus in the constellation Canes Venatici. It was the first galaxy to be classified as a spiral galaxy. Recently it was estimated to be 23 ± 4 million light-years from the Milky Way, but different methods yield distances between 15 and 35 million light-years. Messier 51 is one of the best known galaxies in the sky. The galaxy and its companion, NGC 5195, are easily observed by amateur astronomers, and the two galaxies may even be seen with binoculars. The Whirlpool Galaxy is also a popular target for professional astronomers, who study it to further understand galaxy structure (particularly structure associated with the spiral arms) and galaxy interactions.

Discovery

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).

Visual appearance

Located within the constellation Canes Venatici, M51 is found by following the easternmost star of the Big Dipper, Eta Ursae Majoris, and going 3.5° southwest. Its declination is +47°, making it a circumpolar for observers located above 43°N latitude; it reaches high altitudes throughout the northern hemisphere making it an accessible object from the early hours in winter through the end of spring season, after which observation is hindered in lower latitudes.

M51 is visible through binoculars under dark sky conditions and can be resolved in detail with modern amateur telescopes. When seen through a 100 mm telescope the basic outlines of M51 (limited to 5x6') 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 January 2005 the Hubble Heritage Project constructed a 11477 × 7965-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.

Properties

With the recent SN 2005cs derived estimate of 23 Mly distance, and an angular diameter of roughly 11.2′, it can be inferred that M51's bright circular disk has a radius of about 43,000 light-years. Overall the galaxy is about 35% the size of the Milky Way. Its mass is estimated to be 160 billion solar masses.

A black hole, surrounded by a ring of dust, is thought to exist at the heart of the spiral. The dust ring stands almost perpendicular to the relatively flat spiral nebula. A secondary ring crosses the primary ring on a different axis, a phenomenon that is contrary to expectations. A pair of ionization cones extend from the axis of the main dust ring.

Spiral structure

The very pronounced spiral structure of the Whirlpool Galaxy is believed to be the result of the close interaction between it and its companion galaxy NGC 5195; specifically, its passing through the main disk of M51 about 500 to 600 million years ago. In this model, NGC 5195 came from behind M51 through the disk towards the observer and made another disk crossing as recently as 50 to 100 million years ago until it is where we observe it to be now, slightly behind M51.

Star formation

This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed. (October 2013) (Learn how and when to remove this message)

Stars are usually formed in the center of the galaxy. The center part of M51 appears to be undergoing a period of enhanced star formation. The present efficiency of star formation, defined as the ratio of mass of new stars to the mass of star-forming gas, is only ~1%, quite comparable to the global value for the Milky Way and other galaxies. It is estimated that the current high rate of star formation can last no more than another 100 million years or so.

Induced spiral structure in the larger galaxy is not the only effect of the interaction. Significant compression of hydrogen gas occurs that leads to the development of starbirth regions. In pictures of M51 these show up as the bright blue 'knots' throughout the spiral arms.

Generally speaking, hydrogen gas is the most common component of the interstellar medium (the vast space between stars and planetary systems in galaxies). It exists primarily in its atomic structure and molecular form, and forms huge clouds throughout the entire galaxy. When large sources of gravitational pull pass nearby, such as other galaxies, gravitational interactions produce compression (density) waves that sweep through these hydrogen clouds. This causes some regions of the previously diffuse gas to compress into tight pockets of opaque and dense gas; these are dust lanes one so often sees in the spiral arms. In regions where the concentration and density of gas reaches a critical value, further collapse under its own gravitational pull occurs, and stars are born at the center of the collapse, where the gas is compressed so strongly that fusion initiates.

When this happens, these new-born stars consume huge amounts of gas causing them to expand, shine even hotter, and finally sweep away the surrounding layers of dust and gas by increasing efflux of the stellar wind. The gigantic proportions of the clouds out of which they are born means stars seldom, if ever, are created in isolation. Thus regions of several hot young stars emit sufficient light energy that they can be seen in the high resolution pictures of M51 across millions of lightyears distance.

For an example of such a formation in our own galaxy, see M16, the Eagle Nebula.

Transient events

As of February 2016, three supernovae have been observed in the Whirlpool Galaxy so far. In 1994, supernova SN 1994I was observed in the Whirlpool Galaxy. It was classified as Ic and its brightness peaked at apparent magnitude 12.91.

In June 2005 the type II supernova SN 2005cs was observed in the Whirlpool Galaxy, peaking at apparent magnitude 14.

On 31 May 2011 a type II supernova, was detected in the Whirlpool Galaxy, peaking at magnitude 12.1. This supernova, designated SN 2011dh, showed a spectrum much bluer than average, with P Cygni like characteristics in its hydrogen-Balmer lines. Interestingly, the progenitor was probably a yellow supergiant and not a red or blue supergiant, which is unusual.

Companion

NGC 5195 (also known as Messier 51b or M51b) is a dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC 5194). Both galaxies are located approximately 25 million light-years away in the constellation Canes Venatici. Together, the two galaxies are one of the most famous interacting galaxy pairs.

Galaxy group information

The Whirlpool Galaxy is the brightest galaxy in the M51 Group, a small group of galaxies that also includes M63 (the Sunflower Galaxy), NGC 5023, and NGC 5229. This small group may actually be a subclump at the southeast end of a large, elongated group that includes the M101 Group and the NGC 5866 Group, although most group identification methods and catalogs identify the three groups as separate entities.

See also

• Messier object
• List of Messier objects
• New General Catalogue
• List of galaxies
• NGC 5195 – the companion galaxy to NGC 5194
• Messier 101 – another grand-design spiral galaxy
• M51 in fiction

References

1. Dreyer, J. L. E. (1988). Sinnott, R. W. (ed.). The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters. Sky Publishing Corporation/Cambridge University Press. ISBN 0-933346-51-4.
2. ^ "NASA/IPAC Extragalactic Database". Results for NGC 5194. Retrieved 2006-12-06.
3. ^ Takáts, K.; Vinkó, J. (2006). "Distance estimate and progenitor characteristics of SN 2005cs in M51". Monthly Notices of the Royal Astronomical Society. 372 (4): 1735. arXiv:astro-ph/0608430. Bibcode:2006MNRAS.372.1735T. doi:10.1111/j.1365-2966.2006.10974.x.{{cite journal}}: CS1 maint: unflagged free DOI (link)
4. "Distance Results for MESSIER 051". NASA/IPAC Extragalactic Database. Retrieved 2011-06-06.
5. "M51". SEDS.org.
6. http://www.nasa.gov/multimedia/imagegallery/image_feature_2457.html#.VIX_OGf0DDE Retrieved Dec-2014
7. ^ Arp, H. (1966). "Atlas of Peculiar Galaxies". Astrophysical Journal Supplement. 14: 1–20. Bibcode:1966ApJS...14....1A. doi:10.1086/190147.
8. Elmegreen, D. M.; Elmegreen, B. G. (1987). "Arm classifications for spiral galaxies". Astrophysical Journal. 314: 3–9. Bibcode:1987ApJ...314....3E. doi:10.1086/165034.
9. Matsushita, Satoki; Muller, Sebastien; Lim, Jeremy (9 April 2007). "Jet-disturbed molecular gas near the Seyfert 2 nucleus in M51" (A&A Letters Special Issue). arXiv:0704.0947. Bibcode:2007A&A...468L..49M. doi:10.1051/0004-6361:20067039. {{cite journal}}: Cite journal requires |journal= (help)
10. "Whirlpool Galaxy: First Spiral Galaxy". Universe for Facts. Retrieved 21 December 2014.
11. Scalzi, John (2003). The Rough Guide to the Universe. Rough Guides. p. 250. ISBN 1-85828-939-4.
12. https://messierobjects101.com/messier-object-m51/
13. ^ Nemiroff, R.; Bonnell, J., eds. (2000-07-24). "M51: The Whirlpool Galaxy". Astronomy Picture of the Day. NASA. Retrieved 2007-04-22.
14. Messier, Charles (1781). "Catalogue des Nébuleuses & des amas d'Étoiles". Connaissance des Temps . pp. 227–267 .
15. Hubble, E. P. (1929). "A spiral nebula as a stellar system, Messier 31". Astrophysical Journal. 69: 103–158. Bibcode:1929ApJ....69..103H. doi:10.1086/143167.
16. "Out of This Whirl: the Whirlpool Galaxy (M51) and Companion Galaxy". News Center. HubbleSite. April 25, 2005. Retrieved August 7, 2006.
17. "NASA's Hubble Space Telescope Resolves a Dark "x" Across the Nucleus of M51". News Center. HubbleSite. June 8, 1992. Retrieved August 7, 2006.
18. Salo, Heikki; Laurikainen, Eija (1999). "A Multiple Encounter Model of M51". Astrophysics and Space Science. 269: 663–664. Bibcode:1999Ap&SS.269..663S. doi:10.1023/A:1017002909665.
19. Thronson, Harley A.; Greenhouse, Matthew A. (1988). "Near-Infrared Mass-to-light ratios in Galaxies: Stellar Mass and Star Formation in the Heart of the Whirlpool". The Astrophysical Journal. 327: 671–679. Bibcode:1988ApJ...327..671T. doi:10.1086/166224.
20. Kaler, James B (2001). The Little Book of Stars. New York, NY: Copernicus Books. p. 21. ISBN 0-387-95005-2.
21. "List of Supernovae". Central Bureau for Astronomical Telegrams. Retrieved February 27, 2016.
22. MacRobert, Alan M. (August 24, 2005). "Supernova in M51". Sky Tonight. Sky and Telescope. Retrieved August 7, 2006.
23. Bishop, David. "Supernova 2005cs in M51". supernovae.net. Retrieved August 7, 2006.
24. Bishop, David. "Supernovae 2011dh in M51". supernovae.net (International Supernovae Network). Retrieved 2011-06-06.
25. Kinne (kqr), Richard (2011-06-03). "AAVSO Special Notice #241: New Supernova in M51". AAVSO. Retrieved 2011-06-06.
26. "ATEL 3401: Properties of the Candidate Progenitor of SN 2011dh in M51". Astronomers Telegram. 2011-06-03. Retrieved 2011-06-06.
27. Tully, R. B. (1988). Nearby Galaxies Catalog. Cambridge University Press. ISBN 0-521-35299-1.
28. Fouque, P.; Gourgoulhon, E.; Chamaraux, P.; Paturel, G. (1992). "Groups of galaxies within 80 Mpc. II - The catalogue of groups and group members". Astronomy and Astrophysics Supplement. 93: 211–233. Bibcode:1992A&AS...93..211F.
29. Garcia, A. (1993). "General study of group membership. II - Determination of nearby groups". Astronomy and Astrophysics Supplement. 100: 47–90. Bibcode:1993A&AS..100...47G.
30. Giuricin, G.; Marinoni, C.; Ceriani, L.; Pisani, A. (2000). "Nearby Optical Galaxies: Selection of the Sample and Identification of Groups". Astrophysical Journal. 543 (1): 178–194. arXiv:astro-ph/0001140. Bibcode:2000ApJ...543..178G. doi:10.1086/317070.
31. Ferrarese, L.; Ford, H. C.; Huchra, J.; Kennicutt Jr., R. C.; et al. (2000). "A Database of Cepheid Distance Moduli and Tip of the Red Giant Branch, Globular Cluster Luminosity Function, Planetary Nebula Luminosity Function, and Surface Brightness Fluctuation Data Useful for Distance Determinations". Astrophysical Journal Supplement. 128 (2): 431–459. arXiv:astro-ph/9910501. Bibcode:2000ApJS..128..431F. doi:10.1086/313391.

External links

• StarDate: M51 Fact Sheet
• M51: Calar Alto Observatory
• SEDS: Spiral Galaxy M51
• NASA Astronomy Picture of the Day: M51: The Whirlpool Galaxy in Dust and Stars (10 April 2001)
• Whirlpool Galaxy at ESA/Hubble
• The Whirlpool Galaxy (Messier 51(a)/NGC 5194)
• Servicio de repación oficial Whirlpool
• M51 The Whirlpool Galaxy
• The Whirlpool Galaxy at Constellation Guide
• The Whirlpool Galaxy on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

v t e Messier objects
List	M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13 M14 M15 M16 M17 M18 M19 M20 M21 M22 M23 M24 M25 M26 M27 M28 M29 M30 M31 M32 M33 M34 M35 M36 M37 M38 M39 M40 M41 M42 M43 M44 M45 M46 M47 M48 M49 M50 M51 M52 M53 M54 M55 M56 M57 M58 M59 M60 M61 M62 M63 M64 M65 M66 M67 M68 M69 M70 M71 M72 M73 M74 M75 M76 M77 M78 M79 M80 M81 M82 M83 M84 M85 M86 M87 M88 M89 M90 M91 M92 M93 M94 M95 M96 M97 M98 M99 M100 M101 M102 M103 Added M104 M105 M106 M107 M108 M109 M110
See also	Caldwell catalogue Catalogue of Nebulae and Clusters of Stars Herschel 400 Catalogue Index Catalogue New General Catalogue Revised New General Catalogue
Category Commons Portal

• Unbarred spiral galaxies
• Interacting galaxies
• Peculiar galaxies
• M51 Group
• Canes Venatici (constellation)
• Messier objects
• NGC objects
• UGC objects
• Principal Galaxies Catalogue objects
• Arp objects
• Seyfert galaxies
• Astronomical objects discovered in 1773