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NGC 1261 (also known as Caldwell 87) 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.[3] It is about 10.24[7] billion years old with 341,000[6] 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.[8] Despite this, it has a Shapley–Sawyer Concentration Class of II,[1] indicating a dense central concentration.

NGC 1261
NGC 1261 from Hubble Legacy Archive
Observation data (J2000.0 epoch)
ClassII[1]
ConstellationHorologium
Right ascension03h 12m 16.21s[2]
Declination–55° 12′ 58.4″[2]
Distance53.5 kly (16.4 kpc)[3]
Apparent magnitude (V)8.63[4]
Apparent dimensions (V)12.9′
Physical characteristics
Absolute magnitude−7.81[5]
Mass3.41×105[6] M☉
Metallicity = −1.38±0.14[5] dex
Estimated age10.24 Gyr[7]
Other designationsGCL 5,[4] ESO 155-SC11, Caldwell 87, Melotte 19
See also: Globular cluster, List of globular clusters

A total of 22 RR Lyrae variables have been discovered in this cluster, along with two long-period variables, three SX Phoenicis variables, and an eclipsing binary.[9] It was determined to be an Oosterhoff type I cluster, based on the periods of fourteen of the RR Lyrae variables.[10] 18 probable blue straggler candidates have been identified.[5]


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. 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.
  3. Paust, Nathaniel E. Q.; et al. (February 2010), "The ACS Survey of Galactic Globular Clusters. VIII. Effects of Environment on Globular Cluster Global Mass Functions", The Astronomical Journal, 139 (2): 476–491, Bibcode:2010AJ....139..476P, doi:10.1088/0004-6256/139/2/476, hdl:2152/34371.
  4. "NGC 1261". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-04-08.
  5. Kravtsov, V.; et al. (June 2010), "Wide-field multi-color photometry of the Galactic globular cluster NGC 1261", Astronomy and Astrophysics, 516: 8, arXiv:1005.0007, Bibcode:2010A&A...516A..23K, doi:10.1051/0004-6361/200913449, A23.
  6. 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.
  7. 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.
  8. Simunovic, Mirko; et al. (November 2014), "The Blue Straggler Star Population in NGC 1261: Evidence for a Post-core-collapse Bounce State", The Astrophysical Journal Letters, 795 (1): 5, arXiv:1410.0693, Bibcode:2014ApJ...795L..10S, doi:10.1088/2041-8205/795/1/L10, L10.
  9. Salinas, R.; et al. (September 2016), "An AO-assisted Variability Study of Four Globular Clusters", The Astronomical Journal, 152 (3): 10, arXiv:1605.06517, Bibcode:2016AJ....152...55S, doi:10.3847/0004-6256/152/3/55, 55.
  10. Wehlau, A.; Demers, S. (May 1977), "NGC 1261 and the Oosterhoff type I systems", Astronomy and Astrophysics, 57: 251–256, Bibcode:1977A&A....57..251W.



На других языках

[de] NGC 1261

NGC 1261 ist die Bezeichnung eines Kugelsternhaufen im Sternbild Pendeluhr. Der Sternhaufen hat eine Helligkeit von 8,40 mag und einen Winkeldurchmesser von 6,8 Bogenminuten. Das Objekt wurde am 28. September 1826 vom schottischen Astronomen James Dunlop entdeckt.[3]
- [en] NGC 1261

[es] NGC 1261

NGC 1261 es un cúmulo globular en la constelación de Horologium, distante unos 53.500 años luz de la Tierra. Su magnitud aparente es 8,3. Es un cúmulo bastante concentrado, de clase II.

[ru] NGC 1261

NGC 1261 (другие обозначения — C 87, GCL 5, ESO 155-SC11) — шаровое звёздное скопление в созвездии Часы. Его видимая звёздная величина составляет 8,3m, оно имеет угловой диаметр 6,8' и удалено на 15—17 килопарсек от Земли[1][2].


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