Messier 35

Messier 35 or M35, also known as NGC 2168 or the Shoe-Buckle Cluster, is a relatively close open cluster of stars in the west of Gemini, at about the declination of the Sun when the latter is at June solstice.^[a] It was discovered by Philippe Loys de Chéseaux around 1745 and independently discovered by John Bevis before 1750.^[3] It is scattered over part of the sky almost the size of the full moon and is 2,970 light-years (912 parsecs) away.^[1] The compact open cluster NGC 2158 lies directly southwest of it.

Messier 35
Messier 35 with NGC 2158 at lower right Credit: 2MASS/NASA.
Observation data (J2000 epoch)
Right ascension	06h 08m 54.0s[1]
Declination	+24° 20′ 00″[1]
Distance	2,970 ly (912 pc)[1]
Apparent magnitude (V)	5.3[2]
Apparent dimensions (V)	28[3] arcmins
Physical characteristics
Mass	1,600[4] M☉
Radius	11 ly[5]
Estimated age	100 Myr[6]
Other designations	M35, NGC 2168,[7] Cr 82, C 0605+243
Associations
Constellation	Gemini
See also: Open cluster, List of open clusters

Leonard & Merritt (1989) computed the mass of M35 using a statistical technique based on proper motion velocities of its stars. The mass within the central 3.75 parsecs (12.2 ly) was found to be between 1600 and 3200 solar masses,^[b] consistent with the mass of a realistic stellar population within the same radius.^[8] Bouy et al. in 2015 found a mass of around 1,600 M_☉ within the central 27.5' × 27.5′. There are 305 stars that can be intrinsically shown to be extremely likely to be members,^[c] and up to 4,349 averaging the 50% membership probability, from the kinematic (such as parallax and proper motion) and spectral data published before 2015.^[4] The cluster's metallicity is [Fe/H] = −0.21±0.10, where −1 would be ten times less metallic than the sun.^[4]

Of 418 probable members, Leiner et al. in 2015 found 64 that have variable radial velocities thus are binary star systems.^[9] Four probable members are chemically peculiars, while HD 41995, which in the (telescopic angular) cluster field, shows emission lines.^[10] Hu et al. in 2005 found 13 variable stars in the field; at least three are suspect as cluster members. To be a member means to have a gravitational tie or, if recently freed, having been created by the same event.^[11]

See also

• List of Messier objects