NGC 2129

Open Cluster NGC 2129 (= H VIII.26, h 372, GC 1325; Collinder 77), type d, in Gemini

Right Ascension 06 : 01.0 (h:m)
Declination +23 : 18 (deg:m)
Distance 6.3 (kly)
Visual Brightness 6.7 (mag)
Apparent Dimension 7 (arc min)

Discovered by William Herschel in 1782.

Open cluster NGC 2129 was discovered by William Herschel on February 6, 1782 with his 6.2-inch reflector (7-ft. FL), as one of his early objects found before he started his systematical survey for nebulae and clusters. At this oaccasion, he just noticed but did not catalog this object. During his systematic survey, he found it again on November 16, 1784, with his "standard" instrument, his famous 18.7-inch reflector of 20-ft FL and of Herschelian type (named ahter him). This time, he cataloged it as H VIII.26.

Modern observations determined the parallax determined the distance of this cluster, which was found at about 6,300 light-years (1930 pc), but varies between about 5,900 and 6,700 ly. Its age was estimated at 21 million years. It has been classified as of Shapley class "d" - "Loose Cluster" - and Trumpler type "III,2,p" - detached but not concentrated to center, moderate brightness range of its stars, and poor (less than 50 stars).

.. more to come ..

  • Jean-Claude Mermilliod's WEBDA cluster page for NGC 2129
  • SIMBAD Data of NGC 2129
  • Publications on NGC 2129 (NASA ADS)
  • Observing Reports for NGC 2129 (IAAC Netastrocatalog)
  • NGC Online data for NGC 2129

  • Wikipedia page for NGC 2129

    Hartmut Frommert
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    Last Modification: July 25, 2026