Globular Cluster Koposov 2

Koposov 2
Koposov 2: Globular cluster in Gemini; 500 mm Cassegrain f=3625mm / f7.2; SBIG STL11K; 210+3*50 min LRGB; Bernese Highlands; © 2015 Radek Chromik

History

The very small and extremely faint globular cluster Koposov 2 was discovered together with another globular cluster (Koposov 1) in 2007 by Sergey E. Koposov et al. on the images of the «Sloan Digital Sky Survey Data Release 5». The discovery was then confirmed with deeper imaging with the 2.2 Meter telescope at Calar Alto Observatory. [374]

Physical Properties

The globular cluster is about 33.3 kpc (109'000 light years) away from us and 26.3 kpc (85'800 light years) from the galactic center in the halo of the Milky Way. The diameter of the cluster is about 3 pc (just under 10 light years). Near the center of Koposov 2 we see through it onto a distant background galaxy.

Koposov 2
Koposov 2: Section of SDSS9 (left) and PanSTARRS (right) [147]

Globular clusters are usually one of the oldest structures in the universe and consist of very old stars. However, the age of Koposov 2 is «only» estimated to be around 5 billion (5×109) years. The age of the cluster and its metal content corresponds roughly to that of the Sagittarius dwarf galaxy. This and the low concentration suggest that this is not a real globular cluster, but an open star cluster that the Sagittarius dwarf galaxy has lost. To confirm this, further spectroscopic studies are necessary to determine whether the speed of the cluster matches that of the Sagittarius dwarf galaxy. [375]

Further infos at CDS: Koposov 2

Finder Chart

The globular cluster Koposov 2 is located in the constellation Gemini. The best observation time is October to April.

Chart Globular Cluster Koposov 2
Globular Cluster Koposov 2 in constellation Gemini. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

More Objects Nearby (±15°)

References

147Aladin Lite; aladin.u-strasbg.fr/AladinLite (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
374«The Discovery of Two Extremely Low Luminosity Milky Way Globular Clusters» S. Koposov, J. T. A. de Jong, V. Belokurov, H.-W. Rix, D. B. Zucker, N. W. Evans, G. Gilmore, M. J. Irwin, and E. F. Bell; The Astrophysical Journal, Volume 669, Number 1; arXiv:0706.0019; DOI:10.1086/521422
375«REINVESTIGATING THE CLUSTERS KOPOSOV 1 AND 2» Nathaniel Paust, Danielle Wilson, and Gerard van Belle; Published 2014 June 10; The Astronomical Journal, Volume 148, Number 1; DOI:10.1088/0004-6256/148/1/19