Palomar 12

Palomar 12
Palomar 12
	Palomar 12 by Hubble Space Telescope, 3.36′ view
Observation data (J2000 epoch)
Class	XII
Constellation	Capricornus
Right ascension	21h 46m 38.84s
Declination	–21° 15′ 09.4″
Distance	63.6 ± 2.9 kly (19.50 ± 0.89 kpc)
Apparent magnitude (V)	11.99
Apparent dimensions (V)	17.4′
Physical characteristics
Mass	1.59×104 M☉
Radius	162 ± 8 ly
Metallicity	= –0.85 dex
Estimated age	6.5 Gyr
Notable features	Probably extragalactic
Other designations	GCl 123
	See also: Globular cluster, List of globular clusters

Palomar 12 is a globular cluster in the constellation Capricornus, and is a member of the Palomar Globular Clusters group.

First discovered on the National Geographic Society – Palomar Observatory Sky Survey plates by Robert George Harrington and Fritz Zwicky,^[7] it was initially catalogued as a globular cluster; however, Zwicky came to believe it was actually a nearby dwarf galaxy in the Local Group. It is a relatively young cluster, being about 30% younger than most of the globular clusters in the Milky Way.^[2] It is metal-rich with a metallicity of [Fe/H] ≈ −0.8.^[5] It has an average luminosity distribution of M_v = −4.48.^[8]

Based on proper motion studies, this cluster was first suspected in 2000 to have been captured from the Sagittarius Dwarf Elliptical Galaxy (SagDEG) about 1.7 Ga ago.^[9] It is now generally believed to have originated in that galaxy and is associated with the Sagittarius Stream.^[5] It is estimated to be 6.5 Gyr old.^[5]

References

^ ^a ^b 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.
^ ^a ^b Rosenberg, A.; et al. (1998), "Young Galactic globular clusters II. The case of Palomar 12", Astronomy and Astrophysics, 339: 61–69, arXiv:astro-ph/9809112, Bibcode:1998A&A...339...61R.
^ ^a ^b 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.
^ distance × sin( diameter_angle / 2 ) = 162 ly. radius
^ ^a ^b ^c ^d Geisler, Doug; et al. (September 2007), "Chemical Abundances and Kinematics in Globular Clusters and Local Group Dwarf Galaxies and Their Implications for Formation Theories of the Galactic Halo", The Publications of the Astronomical Society of the Pacific, 119 (859): 939–961, arXiv:0708.0570, Bibcode:2007PASP..119..939G, doi:10.1086/521990, S2CID 119599242.
^ "Cl Pal 12". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 16 November 2006.
^ Abell, George O. (1955). "Globular Clusters and Planetary Nebulae Discovered on the National Geographic Society-Palomar Observatory Sky Survey". Publications of the Astronomical Society of the Pacific. 67 (397): 258. Bibcode:1955PASP...67..258A. doi:10.1086/126815.
^ van den Bergh, Sidney (July 2007). "The Luminosity Distribution of Globular Clusters in Dwarf Galaxies". The Astronomical Journal. 134 (1): 344–345. arXiv:0704.2226. Bibcode:2007AJ....134..344V. doi:10.1086/518868. S2CID 14209616.
^ D. I. Dinescu; S. R. Majewski; T. M. Girard; K. M. Cudworth (2000). "The Absolute Proper Motion of Palomar 12: A Case for Tidal Capture from the Sagittarius Dwarf Spheroidal Galaxy". The Astronomical Journal. 120 (4): 1892–1905. arXiv:astro-ph/0006314. Bibcode:2000AJ....120.1892D. doi:10.1086/301552. S2CID 118898193.

External links

Simbad reference data
SEDS: Palomar 12, Capricornus Dwarf
Palomar 12 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
NASA Astronomy Picture of the Day: Palomar 12 (19 February 2015)

[aj140_6_1830-1] 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, arXiv:1008.2755, Bibcode:2010AJ....140.1830G, doi:10.1088/0004-6256/140/6/1830, S2CID 119183070.

[rosenberg-2] Rosenberg, A.; et al. (1998), "Young Galactic globular clusters II. The case of Palomar 12", Astronomy and Astrophysics, 339: 61–69, arXiv:astro-ph/9809112, Bibcode:1998A&A...339...61R.

[apj742_1_51-3] 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.

[4] stance × sin( diameter_angle / 2 ) = 162 ly. radius

[Geisleretal2007-5] Geisler, Doug; et al. (September 2007), "Chemical Abundances and Kinematics in Globular Clusters and Local Group Dwarf Galaxies and Their Implications for Formation Theories of the Galactic Halo", The Publications of the Astronomical Society of the Pacific, 119 (859): 939–961, arXiv:0708.0570, Bibcode:2007PASP..119..939G, doi:10.1086/521990, S2CID 119599242.

[simbad-6] "Cl Pal 12". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 16 November 2006.

[7] Abell, George O. (1955). "Globular Clusters and Planetary Nebulae Discovered on the National Geographic Society-Palomar Observatory Sky Survey". Publications of the Astronomical Society of the Pacific. 67 (397): 258. Bibcode:1955PASP...67..258A. doi:10.1086/126815.

[Bergh2007-8] van den Bergh, Sidney (July 2007). "The Luminosity Distribution of Globular Clusters in Dwarf Galaxies". The Astronomical Journal. 134 (1): 344–345. arXiv:0704.2226. Bibcode:2007AJ....134..344V. doi:10.1086/518868. S2CID 14209616.

[9] D. I. Dinescu; S. R. Majewski; T. M. Girard; K. M. Cudworth (2000). "The Absolute Proper Motion of Palomar 12: A Case for Tidal Capture from the Sagittarius Dwarf Spheroidal Galaxy". The Astronomical Journal. 120 (4): 1892–1905. arXiv:astro-ph/0006314. Bibcode:2000AJ....120.1892D. doi:10.1086/301552. S2CID 118898193.

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References

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