Messier 2

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Messier 2
Messier2 - HST - Potw1913a.jpg
Messier 2 by Hubble Space Telescope; 2.5′ view
Observation data (J2000 epoch)
Class II [1]
Constellation Aquarius
Right ascension 21h 33m 27.02s [2]
Declination –00° 49′ 23.7″ [2]
Distance 55,000  ly (17  kpc) [3]
Apparent magnitude (V)6.5 [4]
Apparent dimensions (V)16.0′
Physical characteristics
Mass1.04×105 [5]   M☉
Radius87.3 ly [6]
Metallicity  = –1.65 [5] dex
Estimated age12.5  Gyr [7]
Other designations NGC 7089 [8]
See also: Globular cluster, List of globular clusters

Messier 2 or M2 (also designated NGC 7089) is a globular cluster in the constellation Aquarius, five degrees north of the star Beta Aquarii. It was discovered by Jean-Dominique Maraldi in 1746, and is one of the largest known globular clusters.

Contents

Discovery and Visibility

M2 was discovered by the French astronomer Jean-Dominique Maraldi in 1746 [9] while observing a comet with Jacques Cassini. [10] Charles Messier rediscovered it in 1760, but thought that it is a nebula without any stars associated with it. William Herschel, in 1783, was the first to resolve individual stars in the cluster. [11]

M2 is, under extremely good conditions, just visible to the naked eye. Binoculars or a small telescope will identify this cluster as non-stellar, while larger telescopes will resolve individual stars, of which the brightest are of apparent magnitude 6.5. [12]

Characteristics

Chart showing location of M2 M2map.png
Chart showing location of M2

M2 is about 55,000 light-years distant from Earth. At 175 light-years in diameter, it is one of the larger globular clusters known. The cluster is rich, compact, and significantly elliptical. It is 12.5 billion years old and one of the older globular clusters associated with the Milky Way galaxy. [7]

M2 contains about 150,000 stars, including 21 known variable stars. Its brightest stars are red and yellow giant stars. The overall spectral type is F4. [8] M2 is part of the Gaia Sausage, the hypothesized remains of a merged dwarf galaxy. [12]

Data from Gaia has led to the discovery of an extended tidal stellar stream, about 45 degrees long and 300 light-years (100 pc) wide, that is likely associated with M2. It was possibly perturbed due to the presence of the Large Magellanic Cloud. [13]

Location in Universe

Messier 2 is located within our Milky Way galaxy, and is one of the oldest clusters of stars designated to the Milky Way. Like most globular clusters, M2 is found within the galactic halo, specifically in the southern galactic cap. This places it right below the southern pole of the Milky Way. [14]

Oosterhoff Classification

Light curve of an RRab variable star Curva RRab.png
Light curve of an RRab variable star

M2 is defined as an Oosterhoff type II globular cluster. Oosterhoff type is a classification system of globular clusters originally observed by Pieter Oosterhoff in where globular clusters are generally separated into two types. Oosterhoff type is determined by metallicity, age, and average pulsation period of type ab RR Lyrae variable stars of the cluster. A cluster metallicity below −1.6, an age above 13 billion years, [15] and an average RRab Lyrae pulsation period around .64 days indicates a type II cluster. [16] This .64 day value, coupled with a metallicity of −1.65, provides evidence that M2 follows the Oosterhoff Gap phenomena. This is an observed gap in the grouping of type I and type II clusters in the Milky Way on a metallicity vs average RRab pulsation period plot. [17]

M2 is a bit of an anomaly in reference to Oosterhoff type. While it satisfies the metallicity and RRab Lyrae pulsation period conditions, it actually has an age of 12.5 Gyr, well below the cutoff age of 13 Gyr normal for a Oosterhoff type II cluster. This is unexpected because age of a cluster is generally determined from metallicity. However, this abnormality is explained in an article by Marín-Franch. [7]

Related Research Articles

<span class="mw-page-title-main">Globular cluster</span> Spherical collection of stars

A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of member stars, all orbiting in a stable, compact formation. Globular clusters are similar in form to dwarf spheroidal galaxies, and the distinction between the two is not always clear. Their name is derived from Latin globulus. Globular clusters are occasionally known simply as "globulars".

<span class="mw-page-title-main">RR Lyrae variable</span> Type of variable star

RR Lyrae variables are periodic variable stars, commonly found in globular clusters. They are used as standard candles to measure (extra) galactic distances, assisting with the cosmic distance ladder. This class is named after the prototype and brightest example, RR Lyrae.

<span class="mw-page-title-main">Messier 107</span> Globular cluster in Ophiuchus

Messier 107 or M107, also known as NGC 6171 or the Crucifix Cluster, is a very loose globular cluster in a very mildly southern part of the sky close to the equator in Ophiuchus, and is the last such object in the Messier Catalogue.

<span class="mw-page-title-main">Messier 3</span> Globular cluster in the constellation Canes Venatici

Messier 3 is a globular cluster of stars in the northern constellation of Canes Venatici.

<span class="mw-page-title-main">Messier 9</span> Globular cluster in Ophiuchus

Messier 9 or M9 is a globular cluster in the constellation of Ophiuchus. It is positioned in the southern part of the constellation to the southwest of Eta Ophiuchi, and lies atop a dark cloud of dust designated Barnard 64. The cluster was discovered by French astronomer Charles Messier on June 3, 1764, who described it as a "nebula without stars". In 1783, English astronomer William Herschel was able to use his reflector to resolve individual stars within the cluster. He estimated the cluster to be 7–8′ in diameter with stars densely packed near the center.

<span class="mw-page-title-main">Messier 15</span> Globular cluster in the constellation Pegasus

Messier 15 or M15 is a globular cluster in the constellation Pegasus. It was discovered by Jean-Dominique Maraldi in 1746 and included in Charles Messier's catalogue of comet-like objects in 1764. At an estimated 12.5±1.3 billion years old, it is one of the oldest known globular clusters.

<span class="mw-page-title-main">Messier 19</span> Globular cluster in Ophiuchus

Messier 19 or M19 is a globular cluster in the constellation Ophiuchus. It was discovered by Charles Messier on June 5, 1764 and added to his catalogue of comet-like objects that same year. It was resolved into individual stars by William Herschel in 1784. His son, John Herschel, described it as "a superb cluster resolvable into countless stars". The cluster is located 4.5° WSW of Theta Ophiuchi and is just visible as a fuzzy point of light using 50 mm (2.0 in) binoculars. Using a telescope with a 25.4 cm (10.0 in) aperture, the cluster shows an oval appearance with a 3′ × 4′ core and a 5′ × 7′ halo.

<span class="mw-page-title-main">Messier 28</span> Globular cluster in the constellation of Sagittarius

Messier 28 or M28, also known as NGC 6626, is a globular cluster of stars in the center-west of Sagittarius. It was discovered by French astronomer Charles Messier in 1764. He briefly described it as a "nebula containing no star... round, seen with difficulty in 31⁄2-foot telescope; Diam 2′."

<span class="mw-page-title-main">Messier 53</span> Globular cluster in the constellation Coma Berenices

Messier 53 is a globular cluster in the Coma Berenices constellation. It was discovered by Johann Elert Bode in 1775. M53 is one of the more outlying globular clusters, being about 60,000 light-years (18.4 kpc) light-years away from the Galactic Center, and almost the same distance from the Solar System. The cluster has a core radius (rc) of 2.18 pc, a half-light radius (rh) of 5.84 pc, and a tidal radius (rtr) of 239.9 pc.

<span class="mw-page-title-main">Messier 56</span> Globular cluster in the constellation Lyra

Messier 56 is a globular cluster in the constellation Lyra. It was discovered by Charles Messier in 1779. It is angularly found about midway between Albireo and Sulafat. In a good night sky it is tricky to find with large (50–80 mm) binoculars, appearing as a slightly fuzzy star. The cluster can be resolved using a telescope with an aperture of 8 in (20 cm) or larger.

<span class="mw-page-title-main">Messier 62</span> Globular cluster in the constellation Ophiuchus

Messier 62 or M62, also known as NGC 6266 or the Flickering Globular Cluster, is a globular cluster of stars in the south of the equatorial constellation of Ophiuchus. It was discovered in 1771 by Charles Messier, then added to his catalogue eight years later.

<span class="mw-page-title-main">Messier 68</span> Globular cluster in the constellation Hydra

Messier 68 is a globular cluster found in the east south-east of Hydra, away from its precisely equatorial part. It was discovered by Charles Messier in 1780. William Herschel described it as "a beautiful cluster of stars, extremely rich, and so compressed that most of the stars are blended together". His son John noted that it was "all clearly resolved into stars of 12th magnitude, very loose and ragged at the borders".

<span class="mw-page-title-main">Messier 75</span> Globular cluster in the constellation Sagittarius

Messier 75 or M75, also known as NGC 6864, is a giant globular cluster of stars in the southern constellation Sagittarius. It was discovered by Pierre Méchain in 1780 and included in Charles Messier's catalog of comet-like objects that same year.

<span class="mw-page-title-main">Messier 92</span> Globular cluster in the constellation Hercules

Messier 92 is a globular cluster of stars in the northern constellation of Hercules.

<span class="mw-page-title-main">NGC 6934</span> Globular cluster in the constellation Delphinus

NGC 6934 is a globular cluster of stars in the northern constellation of Delphinus, about 52 kilolight-years distant from the Sun. It was discovered by the German-born astronomer William Herschel on 24 September 1785. The cluster is following a highly eccentric orbit through the Milky Way along an orbital plane that is inclined by 73° to the galactic plane. It may share a common dynamic origin with NGC 5466. As of 2018, it has been poorly studied.

<span class="mw-page-title-main">NGC 1261</span> Globular cluster in the constellation Horologium

NGC 1261 is a globular cluster of stars in the southern constellation of Horologium, first discovered by Scottish astronomer James Dunlop in 1826. The cluster is located at a distance of 53 kilolight-years from the Sun, and 59 kilolight-years from the Galactic Center. It is about 10.24 billion years old with 341,000 times the mass of the Sun. The cluster does not display the normal indications of core collapse, but evidence suggests it may have instead passed through a post core-collapse bounce state within the past two billion years. The central luminosity density is 2.22 L☉·pc−3, which is low for a globular cluster. Despite this, it has a Shapley–Sawyer Concentration Class of II, indicating a dense central concentration.

<span class="mw-page-title-main">NGC 4147</span> Globular cluster in the constellation Coma Berenices

NGC 4147 is the New General Catalogue identifier for a globular cluster of stars in the northern constellation of Coma Berenices. It was discovered by English astronomer William Herschel on March 14, 1784, who described it as "very bright, pretty large, gradually brighter in the middle". With an apparent visual magnitude of 10.7, it is located around 60,000 light years away from the Sun at a relatively high galactic latitude of 77.2°.

<span class="mw-page-title-main">NGC 6441</span> Globular cluster in Scorpius

NGC 6441 is a globular cluster in the southern constellation of Scorpius. It was discovered by the Scottish astronomer James Dunlop on May 13, 1826, who described it as "a small, well-defined rather bright nebula, about 20″ in diameter". The cluster is located 5 arc minutes east-northeast of the star G Scorpii, and is some 43,000 light-years from the Sun.

<span class="mw-page-title-main">NGC 5053</span> Globular cluster in the constellation Coma Berenices

NGC 5053 is the New General Catalogue designation for a globular cluster in the northern constellation of Coma Berenices. It was discovered by German-British astronomer William Herschel on March 14, 1784 and cataloged as VI-7. In his abbreviated notation, he described it as, "an extremely faint cluster of extremely small stars with resolvable nebula 8 or 10′ diameter, verified by a power of 240, beyond doubt". Danish-Irish astronomer John Louis Emil Dreyer reported in 1888 that the cluster appeared, "very faint, pretty large, irregular round shape, growing very gradually brighter at the middle".

<span class="mw-page-title-main">Gaia Sausage</span> Remains galaxy merger in the Milky Way

The Gaia Sausage or Gaia Enceladus is the remains of a dwarf galaxy that merged with the Milky Way about 8–11 billion years ago. At least eight globular clusters were added to the Milky Way along with 50 billion solar masses of stars, gas and dark matter. It represents the last major merger of the Milky Way.

References

  1. ↑ Shapley, Harlow; Sawyer, Helen B. (August 1927). "A Classification of Globular Clusters". Harvard College Observatory Bulletin. 849 (849): 11–14. Bibcode:1927BHarO.849...11S.
  2. 1 2 Goldsbury, Ryan; et al. (December 2010). "The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters". The Astronomical Journal. 140 (6): 1830–1837. arXiv: 1008.2755 . Bibcode:2010AJ....140.1830G. doi:10.1088/0004-6256/140/6/1830. S2CID   119183070.
  3. ↑ Helmi, A; van Leeuwen, F; McMillan, P J; Massari, D; Antoja, T; Robin, A; Lindegren, L; Bastian, U (2018). Gaia Collaboration. "Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way". Astronomy and Astrophysics. 616: A12. arXiv: 1804.09381 . Bibcode:2018A&A...616A..12G. doi:10.1051/0004-6361/201832698. S2CID   260496632.
  4. ↑ "Messier 2". SEDS Messier Catalog. Archived from the original on 27 June 2023. Retrieved 27 April 2022.
  5. 1 2 Boyles, J.; et al. (November 2011). "Young Radio Pulsars in Galactic Globular Clusters". The Astrophysical Journal. 742 (1): 51. arXiv: 1108.4402 . Bibcode:2011ApJ...742...51B. doi:10.1088/0004-637X/742/1/51. S2CID   118649860.
  6. ↑ distance × sin( diameter_angle / 2 ) = 87.3 ly. radius
  7. 1 2 3 Marín-Franch, Antonio; Aparicio, Antonio; Piotto, Giampaolo; Rosenberg, Alfred; Chaboyer, Brian; Sarajedini, Ata; Siegel, Michael; Anderson, Jay; Bedin, Luigi R.; Dotter, Aaron; Hempel, Maren; King, Ivan; Majewski, Steven; Milone, Antonino P.; Paust, Nathaniel; Reid, I. Neill (2009). "The ACS Survey of Galactic Globular Clusters. VII. Relative Ages". The Astrophysical Journal. 694 (2): 1498. arXiv: 0812.4541 . Bibcode:2009ApJ...694.1498M. doi:10.1088/0004-637X/694/2/1498. S2CID   118407466.
  8. 1 2 "M 2". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2006-11-15.
  9. ↑ Stephen James O'Meara (7 April 2014). Deep-Sky Companions: The Messier Objects. Cambridge University Press. pp. 47–. ISBN   978-1-107-01837-2.
  10. ↑ "THE GLOBULAR CLUSTER M2 – Astronomy Magazine – Interactive Star Charts, Planets, Meteors, Comets, Telescopes". cs.astronomy.com. Retrieved 2023-04-29.
  11. ↑ admin (2015-01-17). "Messier 2". Messier Objects. Retrieved 2023-04-29.
  12. 1 2 Myeong, G. C; Evans, N. W; Belokurov, V; Sanders, J. L; Koposov, S. E (2018). "The Sausage Globular Clusters". The Astrophysical Journal. 863 (2): L28. arXiv: 1805.00453 . Bibcode:2018ApJ...863L..28M. doi: 10.3847/2041-8213/aad7f7 . S2CID   67791285.
  13. ↑ Grillmair, Carl J. (2022). "The Extended Tidal Tails of NGC 7089 (M2)". The Astrophysical Journal. 929 (1): 89. arXiv: 2203.04425 . Bibcode:2022ApJ...929...89G. doi: 10.3847/1538-4357/ac5bd7 . S2CID   247318732.
  14. ↑ info@noirlab.edu. "M2, NGC 7089". www.noirlab.edu. Retrieved 2023-04-29.
  15. ↑ van den Bergh, Sidney (2011). "Some Systematics of Galactic Globular Clusters". Publications of the Astronomical Society of the Pacific. 123 (907): 1044–1053. arXiv: 1108.0708 . Bibcode:2011PASP..123.1044V. doi: 10.1086/662132 . ISSN   0004-6280.
  16. ↑ Stobie, R. S. (1971). "On the Difference Between the Oosterhoff Types i and II Globular Clusters". The Astrophysical Journal. 168: 381. Bibcode:1971ApJ...168..381S. doi:10.1086/151094.
  17. ↑ Kuehn, Charles A.; Smith, Horace A.; Catelan, Marcio; Jeon, Young-Beom; Nemec, James M.; Walker, Alistair R.; Kunder, Andrea; Dame, Kyra; Pritzl, Barton J.; De Lee, Nathan; Borissova, Jura (2013-10-01). "RR Lyrae in the LMC: Insights Into the Oosterhoff Phenomenon". arXiv: 1310.0553 [astro-ph.SR].

See also

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