Astronomy:NGC 1261
| NGC 1261 | |
|---|---|
 NGC 1261 from Hubble Legacy Archive | |
| Observation data (J2000.0 epoch) | |
| Class | II[1] |
| Constellation | Horologium |
| Right ascension | 03h 12m 16.21s[2] |
| Declination | –55° 12′ 58.4″[2] |
| Distance | 53.5 kly (16.4 kpc)[3] |
| Apparent magnitude (V) | 8.63[4] |
| Apparent dimensions (V) | 12.9′ |
| Physical characteristics | |
| Absolute magnitude | −7.81[5] |
| Mass | 3.41×105[6] M☉ |
| Metallicity | [math]\displaystyle{ \begin{smallmatrix}\left[\ce{Fe}/\ce{H}\right]\end{smallmatrix} }[/math] = −1.38±0.14[5] dex |
| Estimated age | 10.24 Gyr[7] |
| Other designations | GCL 5,[4] ESO 155-SC11, Caldwell 87, Melotte 19 |
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.
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
- ↑ 1.0 1.1 Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin 849 (849): 11–14, Bibcode: 1927BHarO.849...11S.
- ↑ 2.0 2.1 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, doi:10.1088/0004-6256/140/6/1830, Bibcode: 2010AJ....140.1830G.
- ↑ 3.0 3.1 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, doi:10.1088/0004-6256/139/2/476, Bibcode: 2010AJ....139..476P.
- ↑ 4.0 4.1 "NGC 1261". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NGC+1261.
- ↑ 5.0 5.1 5.2 Kravtsov, V. et al. (June 2010), "Wide-field multi-color photometry of the Galactic globular cluster NGC 1261", Astronomy and Astrophysics 516: 8, doi:10.1051/0004-6361/200913449, A23, Bibcode: 2010A&A...516A..23K.
- ↑ 6.0 6.1 Boyles, J. et al. (November 2011), "Young Radio Pulsars in Galactic Globular Clusters", The Astrophysical Journal 742 (1): 51, doi:10.1088/0004-637X/742/1/51, Bibcode: 2011ApJ...742...51B.
- ↑ 7.0 7.1 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, doi:10.1111/j.1365-2966.2010.16373.x, Bibcode: 2010MNRAS.404.1203F.
- ↑ 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, doi:10.1088/2041-8205/795/1/L10, L10, Bibcode: 2014ApJ...795L..10S.
- ↑ Salinas, R. et al. (September 2016), "An AO-assisted Variability Study of Four Globular Clusters", The Astronomical Journal 152 (3): 10, doi:10.3847/0004-6256/152/3/55, 55, Bibcode: 2016AJ....152...55S.
- ↑ 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.
External links
- NGC 1261 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
- SEDS
- NASA data
- Photometry paper
- Globular Clusters Database
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