Palomar 12

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Palomar 12
Observation data (J2000 epoch)
Class XII
Constellation Capricornus
Right ascension 21h 46m 38.8s[1]
Declination −21° 15′ 03″[1]
Distance 64 ± 3 kly (19.5 ± 0.9 kpc[2])
Apparent magnitude (V) 11.99
Apparent dimensions (V) 17′.4
Physical characteristics
Mass - kg (- M{\odot})
Radius 162 ± 8 ly[3]
VHB -
Estimated age 6.5 Gyr[4]
Notable features -
Other designations GCl 123[1]
See also: Globular cluster, List of globular clusters
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Palomar 12 is a globular cluster in the constellation Capricornus that belongs to the halo of the Milky Way galaxy. First discovered on the Palomar Survey Sky plates by Robert G. Harrington and Fritz Zwicky,[5] it was catalogued as a globular cluster. However Zwicky came to believe this 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.[4] It has an average luminosity distribution of Mv = -4.48.[6]

Based on proper motion studies, this cluster was first suspected in 2000 to have been captured from the Sagittarius dwarf galaxy about 1.7 Gyr ago.[7] Its membership is now generally believed (Cohen 2004, Sbordone et al. 2006).[4]

[edit] References

  1. ^ a b c SIMBAD Astronomical Database. Results for Palomar 12. Retrieved on 2006-11-16.
  2. ^ a b A. Rosenberg, I. Saviane, G. Piotto, E. V. Held (1998). "Young Galactic globular clusters II. The case of Palomar 12". Astronomy and Astrophysics 339: 61–69. 
  3. ^ distance × sin( diameter_angle / 2 ) = 162 ly. radius
  4. ^ a b c Geisler, Doug; Wallerstein, George; Smith, Verne V. & Casetti-Dinescu, Dana I. (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, <http://adsabs.harvard.edu/abs/2007PASP..119..939G> 
  5. ^ 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. doi:10.1086/126815. 
  6. ^ van den Bergh, Sidney (July 2007), “The Luminosity Distribution of Globular Clusters in Dwarf Galaxies”, The Astronomical Journal 134 (1): 344-345, <http://adsabs.harvard.edu/abs/2007AJ....134..344V> 
  7. ^ 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. doi:10.1086/301552. 

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