A Selection of Double Stars in Cancer
April 2008 :
For our spring double star selection, we’ll say goodbye to Gemini and shift eastward to the faint constellation Cancer. Notable for its bright Messier cluster M44 (the Praesepe), Cancer is also home to a splendid array of double and multiple stars. How many can you notch? (Data from the Washington Double Star Catalog (WDS)
Struve 1177 magnitudes 6.7 and 7.4, separation 3.5”, Position Angle 350o (2003) This pretty pair is located near the Cancer/Gemini border just a half degree southeast of chi Geminorum. Use 150X or more for a clean split.
zeta (Struve 1196) mags 5.1 and 6.2, sep 5.9”, p.a. 72o (2004) Zeta is a fine double for small scopes and a grand triple for instruments of 6-inch aperture or more. The primary is a close binary with a period of 60 years; mags 5.3 and 6.3, currently widening to a separation of 1.0” (P.A 55o). If you have a 6-inch scope or larger, give it a try!
24 (Struve 1224) mags 6.9 and 7.5, sep 5.7”, P.A. 51o (2003) 24 Cancri is the western-most member of an attractive row of stars found 4 degrees northwest of M44. A delicate beauty!
phi2 (Struve 1223) mags 6.2 and 6.2, sep 5.2”, P.A. 218o (2003) Close, equally bright double stars are among the night sky’s loveliest sights. This set of pure-white twins gleams at us from the darkness of space like the eyes of a distant cosmic cat. A must-see object.
Struve 1245 mags 6.0 and 7.2, sep 10.0”, P. A. 25o (2004) This striking double star is located on the southern boundary of Cancer, just one degree north of the star delta Hydrae.
iota1 (Struve 1268) mags 4.1 and 6.0, sep 30.7”, P.A. 308o (2003) A showpiece double noted for its gold and blue colors – a springtime version of Albireo. In the same field, one-half degree to the southwest, is the faint pair Struve 1266; mags 8.8 and 10.0, 23.4”, 65o (2003)
iota2 (57) (Struve 1291) mags 6.1 and 6.4, sep 1.5”, P.A. 311o (2004) Test object for a 3-inch scope - save for optimum seeing conditions. A third component, mag 9.2 lies 54.5” away in a P.A. of 203o (1988).
sigma4 (66) (Struve 1298) mags 6.0 and 8.6, sep 4.5”, P.A. 134o (2003) The magnitude difference will make this duo a bit of a challenge in small scopes. Use the highest magnification seeing conditions will allow.
