Degree of difficulty 2 (of 5)

Minimum aperture Naked eye

Designation NGC 2168

Type Open cluster

Class III3r

Distance 2710 ly (K2005) 3590 ly (2004) 2940 ly (CMD, 2003) 2660 ly (proper motion, 2002)

Size 22 ly

Constellation Gemini

R.A. 6h 8.9min

Decl. +24° 20′

Magnitude 5.1

Surface brightness –

Apparent diameter 28′

Discoverer de Chéseaux, 1746

History The star cluster M 35 was discovered in 1745 or 1746 by Phillippe Loys de Chéseaux. However, the observations of this Swiss observer were not published. The Englishman John Bevis made an independent discovery of this cluster before 1750. That observation was known to Charles Messier, when he noted on the 30th of August 1764: “Cluster of very small stars, near the left foot of Castor, at little distance from the stars μ & η of this constellation.”

Smyth calls M 35 a “gorgeous field of stars from the 9th to the 16th magnitudes” and remarks: “the small stars being inclined to form curves of three or four, and often with a large one at the root of the curve.” John Herschel, using a much larger aperture and a smaller field of view, was a little less impressed with the view: “A large, coarse, pretty rich cluster of stars of 9th to 16th magnitude, which fills 2 or 3 fields, but chiefly one in which are about 100 stars.”

Lassell, observing with an aperture of 24 inches, commented: “field of view is perfectly filled with brilliant stars, of exquisite beauty.” Lord Rosse counted about 300 stars in a field of 26′. A century ago, Leo Brenner remarked: “Splendid object, in particular in larger scopes. The entire field of view of 20′ is littered with stars of 8th to 12th magnitude, all very close to each other.”