M-35
Open star cluster M35 is consisted of over 200 stars (of which Wallenquist has counted 120 brighter than mag 13) scattered over the area covered by the full Moon (30'). At its distance of 2,800 light years, this corresponds to a linear diameter of about 24 light years; its central density is about 6.21 stars per cubic parsec. Some authors have estimated a larger diameter of up to 46' (H. Shapley in 1930). With about 110 million years, it is of intermediate age, and contains some post-main sequence stars (including several yellow and orange giants of spectral type late G to early K). Its hottest main sequence star is given as of spectral class B3 (Sky Catalog 2000), and its Trumpler classification as III,3,r by all sources. It is approaching us at 5 km/sec.
Even the naked eye finds this cluster easily near the 3 "foot stars" of Gemini under fairly good observing conditions. The slightest optical instrument will resolve the brighter stars and make it a splendid view at low magnifications, a nearly circular cluster with rather uniform stellar distribution. Amateurs with more powerful telescopes can view its fainter neighbor, NGC 2158 (at the upper left in our image).