Palomar 12 globular cluster

Palomar 12 is a globular cluster in the constellation Capricornus [1]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, 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. It is metal-rich with a metallicity of [Fe/H] ~= -0.8.[5] It has an average luminosity distribution of Mv = -4.48.

Based on proper motion studies, this cluster was first suspected in 2000 to have been captured from the Sagittarius dwarf galaxy about 1.7 Ga ago. It is now generally believed to be a member of the Sagittarius dwarf galaxy (Cohen 2004, Sbordone et al. 2006). It is estimated to be 6.5 Gyr old.

Palomar 12

[1] Constellations seen from planet Earth
 * Class XII
 * Constellation Capricornus
 * Right ascension 21h 46m 38.84s
 * Declination –21° 15′ 09.4″
 * Distance 63.6 ± 2.9 kly (19.5 ± 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[3] dex
 * Estimated age 6.5 Gyr
 * Other designations GCl 123