Palomar 12
Globular cluster in the constellation Capricornus
From Wikipedia, the free encyclopedia
Palomar 12 is a globular cluster in the constellation Capricornus, and is a member of the Palomar Globular Clusters group.
| 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[1] |
| Declination | –21° 15′ 09.4″[1] |
| Distance | 63.6 ± 2.9 kly (19.50 ± 0.89 kpc)[2] |
| Apparent magnitude (V) | 11.99 |
| Apparent dimensions (V) | 17.4′ |
| Physical characteristics | |
| Mass | 1.59×104[3] M☉ |
| Radius | 162 ± 8 ly[4] |
| Metallicity | [Fe/H] = –0.85[3] dex |
| Estimated age | 6.5 Gyr[5] |
| Notable features | Probably extragalactic |
| Other designations | GCl 123[6] |
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 Mv = −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]
