Messier 92
Messier 92 | |
---|---|
Observation data (J2000epoch) | |
Class | IV[1] |
Constellation | Hercules |
Right ascension | 17h17m07.39s[2] |
Declination | +43° 08′ 09.4″[2] |
Distance | 26.7×10 3ly(8.2kpc)[3] |
Apparent magnitude(V) | 6.4[4] |
Apparent dimensions(V) | 14' arc minutes |
Physical characteristics | |
Mass | 2.0×105[5]M☉ |
Radius | 54ly[6] |
Metallicity | = –2.32[7]dex |
Estimated age | 14.2 Gyr[8] |
Other designations | M92,NGC6341, GCl 59[9] |
Messier 92(also known asM92,M 92,orNGC 6341) is aglobular clusterof stars in the northernconstellationofHercules.
Discovery
[edit]It was discovered byJohann Elert Bodeon December 27, 1777, then published in theBerliner Astronomisches Jahrbuchduring 1779.[10][11]It was inadvertently rediscovered byCharles Messieron March 18, 1781,[a]and added as the 92nd entry in his catalogue.[12]William Herschel first resolved individual stars in 1783.
Visibility
[edit]It is one of the brighter of its sort in apparent magnitude in the northern hemisphere and in itsabsolute magnitudeinthe galaxy,but it is often overlooked by amateur astronomers due to angular proximity to bright clusterMessier 13,about 20% closer. Though when compared to M13, M92 is only slightly less bright, but about 1/3 less extended. It is visible to the naked eye under very good viewing conditions.[13]With a small telescope, M92 can be seen as a nebulous smudge even in a severely light-polluted sky, and can be further resolved in darker conditions.
Characteristics
[edit]It is also one of the galaxy's oldest clusters. It is around 16×10 3ly(4.9kpc) above/below thegalactic planeand 33×10 3ly (10 kpc) from theGalactic Center.[14]It is about 26,700light-yearsaway from theSolar System.The half-light radius, or radius containing the upper half of its light emission, is 1.09arcminutes(′), while the tidal radius, the broadest standard measure, is 15.17′.It appears onlyslightly flattened:its minor axis is about 89% ± 3% of the major.[3]
Characteristic of other globulars, it has little of the elements other than hydrogen and helium; astronomers term this lowmetallicity.Specifically, relative to theSun,its iron abundance is [Fe/H] = –2.32dex,[14]which is 0.5% of 1.0, on thislogarithmicscale, the solar abundance.[15]This puts the estimated age range for the cluster at11 ± 1.5 billion years.[16]
Its true diameter is 108 ly, and may have a mass corresponding to 330,000 suns.[17]
The cluster is not yet in, nor guaranteed to undergo,core collapseand the core radius figures as about 2arcseconds(″).[14]It is anOosterhofftype II (OoII) globular cluster, which means it belongs to the group of metal-poor clusters with longer periodRR Lyrae variablestars. The 1997Catalogue of Variable Stars in Globular Clusterslisted 28 candidate variable stars in the cluster, although only 20 have been confirmed. As of 2001, there are 17 known RR Lyrae variables in Messier 92.[18]10 X-ray sources have been detected within the 1.02 arcminute half-mass radius of the cluster, of which half are candidatecataclysmic variable stars.[19][20]
M92 is approaching us at 112 km/sec. Its coordinates indicate that the Earth's NorthCelestial Poleperiodically passes less than one degree of this cluster during the precession of Earth's axis. Thus, M92 was a "Polarissima Borealis", or "North Cluster", about 12,000 years ago (10,000 BC), and it will again in about 14,000 years (16,000 AD).[17]
The multiple stellar populations in this cluster, revealing that it hosts at least two stellar generations of stars named 1G and 2G, as well as two distinct groups of 2G stars (2GA and 2GB).[21]The helium abundances of 2GA and 2GB stars have higher mass fractions than that of the 1G stars by 0.01 and 0.04, respectively.
Gallery
[edit]-
Messier 92 - wide field view from theIsaac Newton Group of Telescopes
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Map showing how Messier 92 figures in the two-dimensional sky, in the east of Hercules. Maps set by convention against a southern horizon, such that east is left.
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Messier 92 by theSloan Digital Sky Survey
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Messier 92 byHST;3.5′view
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Messier 92 captured by theJames Webb Space Telescope’sNIRCam instrument
See also
[edit]References and footnotes
[edit]- ^Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters",Harvard College Observatory Bulletin,849(849): 11–14,Bibcode:1927BHarO.849...11S.
- ^abGoldsbury, Ryan; et al. (December 2010), "The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters [ Erratum: 2011AJ....142...66G ]",The Astronomical Journal,140(6): 1830–1837,arXiv:1008.2755,Bibcode:2010AJ....140.1830G,doi:10.1088/0004-6256/140/6/1830,S2CID119183070
- ^abChen, C. W.; Chen, W. P. (October 2010), "Morphological Distortion of Galactic Globular Clusters",The Astrophysical Journal,721(2): 1790–1819,Bibcode:2010ApJ...721.1790C,doi:10.1088/0004-637X/721/2/1790
- ^"Messier 92".SEDS Messier Catalog.Retrieved30 April2022.
- ^Marks, Michael; Kroupa, Pavel (August 2010), "Initial conditions for globular clusters and assembly of the old globular cluster population of the Milky Way",Monthly Notices of the Royal Astronomical Society,406(3): 2000–2012,arXiv:1004.2255,Bibcode:2010MNRAS.406.2000M,doi:10.1111/j.1365-2966.2010.16813.x,S2CID118652005.Mass is from MPDon Table 1.
- ^distance × sin( diameter_angle / 2 ) = 54 ly. radius
- ^Forbes, Duncan A.; Bridges, Terry (May 2010), "Accreted versus in situ Milky Way globular clusters",Monthly Notices of the Royal Astronomical Society,404(3): 1203–1214,arXiv:1001.4289,Bibcode:2010MNRAS.404.1203F,doi:10.1111/j.1365-2966.2010.16373.x,S2CID51825384.
- ^Paust, Nathaniel E. Q.; Chaboyer, Brian; Sarajedini, Ata (June 2007), "BVI Photometry and the Luminosity Functions of the Globular Cluster M92",The Astronomical Journal,133(6): 2787–2798,arXiv:astro-ph/0703167,Bibcode:2007AJ....133.2787P,doi:10.1086/513511,S2CID13160815
- ^"M 92".SIMBAD.Centre de données astronomiques de Strasbourg.Retrieved2006-11-17.
- ^Bode (1779). "Zweyter Theil 20. Beobachtung des Kometen von 1779 und Entdeckung einiger neuen Nebelsterne [Second Part. 20. Observation of the comet of 1779 and discovery of some new nebulae]".Astronomisches Jahrbuch oder Ephemeriden für das Jahr 1782[Astronomical Yearbook or Ephemerides for the Year 1782.] (in German). Berlin, (Germany): George Jacob Decker. p. 156.From p. 156:"[…] ich am 27. Decemb. 1777 einenneuen,mir nicht bekanntenNebelfleck im Herkules,südwestlich unter dem Stern ⍳ an dessen Fusse entdeckt, der sich in einer mehrentheils runden Figur mit einem blassen Lichtschimmer zeigt. "( […] on the 27th December 1777, I discovered anew nebula,which was unknown to me,in Hercules,southwest under the star ⍳ [iota] at his feet, which appears as a mostly round shape with a pale glimmer.)
- ^Kanas, Nick (2007),Star maps: history, artistry, and cartography,Springer-Praxis books in popular astronomy, Springer, p. 180,ISBN978-0387716688
- ^Garfinkle, Robert A. (1997),Star-Hopping: Your Visa to Viewing the Universe,Cambridge University Press,p. 131,ISBN978-0521598897
- ^Frommert, Hartmut; Kronberg, Christine (September 2, 2007),"Messier 92",SEDS,The Munich Astro Archive, archived fromthe originalon 2016-03-04,retrieved2012-04-08
- ^abcDrukier, G. A.; et al. (March 2007), "The Global Kinematics of the Globular Cluster M92",The Astronomical Journal,133(3): 1041–1057,arXiv:astro-ph/0611246,Bibcode:2007AJ....133.1041D,doi:10.1086/510721,S2CID15452502
- ^Since 10−2.29= 0.00513.
- ^Di Cecco, A.; Becucci, R.; Bono, G.; Monelli, M.; Stetson, P. B.; Degl'Innocenti, S.; Moroni, P. G. Prada; Nonino, M.; Weiss, A.; Buonanno, R.; Calamida, A. (2010-06-27)."On the absolute age of the Globular Cluster M92".Publications of the Astronomical Society of the Pacific.122(895): 991–999.arXiv:1006.5217.Bibcode:2010PASP..122..991D.doi:10.1086/656017.
- ^ab"Messier Object 92".messier.seds.org.Retrieved2022-05-28.
- ^Kopacki, G. (2003), "Variable stars in the globular cluster M 92",Astronomy and Astrophysics,369(3): 862–870,arXiv:astro-ph/0211042,Bibcode:2001A&A...369..862K,doi:10.1051/0004-6361:20010155,S2CID116811988
- ^Lu, Ting-Ni; et al. (August 2011),"Chandra and HST Studies of the X-Ray Sources in Galactic Globular Cluster M92"(PDF),The Astrophysical Journal,736(2): 158,Bibcode:2011ApJ...736..158L,doi:10.1088/0004-637X/736/2/158,hdl:1721.1/95659,S2CID54766335
- ^Ferraro, F. R.; Paltrinieri, B.; Fusi Pecci, F.; Rood, R. T.; Dorman, B. (1998-01-01)."Faint UV Objects in the Core of Ggcs: a New Subclass of Cvs?".Ultraviolet Astrophysics Beyond the IUE Final Archive.413:561.Bibcode:1998ESASP.413..561F.
- ^World, FTT."Astronomers discover new insights into multiple stellar populations in Messier 92 using James Webb".
- ^On March 18
External links
[edit]- Messier 92 onWikiSky:DSS2,SDSS,GALEX,IRAS,Hydrogen α,X-Ray,Astrophoto,Sky Map,Articles and images
- Messier 92 @ SEDS Messier pages
- Messier 92, Galactic Globular Clusters Database page
- Merrifield, Michael; Crowther, Paul."M92 – Globular Cluster".Deep Sky Videos.Brady Haran.
- NASA Astronomy Picture of the Day: Comet Garradd and M92 (4 February 2012)