Capricornus Dwarf, Palomar 12

RA:

21 : 46.6

Dec:

-21 : 15

Type:

Globular Cluster

RV:

+27.8 km/s :

Distance:

62.0 kly

Apparent Dimension:

2.9 arc min

Diameter:

Brightness:

11.7 mag vis

Abs. Mag:

Mass:

This object was discovered by R.G. Harrington and Fritz Zwicky. George Abell cataloged it as a globular cluster in 1955, known as Palomar 12. Unaware of this, or in doubt about this classification, it was later classified as a dwarf spheroidal galaxy by Fritz Zwicky in 1957, and named the Capricornus Dwarf; it was supposed to be a Local Group member candidate because of its resolution into stars. It was included as Anon 2144 in the First Reference Catalogue of Bright Galaxies (RC I), where it was classfied as "E0?pec", and in the UGCA catalog as UGCA 421. Notably, Zwicky cataloged it with a wrong sign in declination. Later it was confirmed that this is actually a remote globular cluster within our Milky Way galaxy.

Palomar 12 lies out at about 62,000 light years from us and 52,000 light years from the Galactic Center. It is receding from us at about 28 km/s.

Irwin (1999) has brought up the hypothesis that Palomar 12 may once have been a member of SagDEG which has escaped somewhen in the past and since been integrated in the Galactic Globular Cluster system and thus the Milky Way's Halo.

References:

• George O. Abell, 1955. Globular Clusters and Planetary Nebulae Discovered on the National Geographic Society-Palomar Observatory Sky Survey. Publications of the Astronomical Society of the Pacific, Vol. 67, No. 397, p. 258 (August 1955) [ADS: 1955PASP...67..258A]
• Irwin, 1999.
• Fritz Zwicky, 1957. Morphological astronomy. Springer Verlag.

Last Modification: May 20, 2000