Palomar 12
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| 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: | - (- M☉) |
| Radius: | 162 ± 8 ly[3] |
| VHB: | - |
| Estimated age: | 9 ± 1 Gyr[2][4] |
| Notable features: | - |
| Other designations: | GCl 123[1] |
| See also: Globular cluster, List of globular clusters | |
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]
Based on proper motion studies, this cluster may have been captured from the Sagittarius dwarf galaxy about 1.7 Gyr ago.[6]
[edit] References
- ^ a b c SIMBAD Astronomical Database. Results for Palomar 12. Retrieved on 2006-11-16.
- ^ a b c 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.
- ^ distance × sin( diameter_angle / 2 ) = 162 ly. radius
- ^ 68% ± 10% the age of M5 and 47 Tuc
- ^ 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.
- ^ 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.
[edit] External links
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