A Selection of Double Stars in Cygnus
October 2007 :
Although it’s a Summer Triangle constellation, Cygnus remains well-seen throughout the autumn months. Located in the star-rich fields of the Milky Way, the Swan is home to numerous double stars. Here are eight of the most noteworthy (data from the Washington Double Star Catalog (WDS):
beta Cygni (Albireo) magnitudes 3.4 and 4.7, separation 34.7”, Position Angle 55o (2003)
Arguably the finest double star in the northern sky, Albireo boasts hues of topaz yellow and sapphire blue. Colors actually appear more vivid in small scopes.
16 Cygni mags 6.0 and 6.2, sep 39.1”, p.a. 134o (2003)
Attractive set of yellowish “twins.” About a degree eastward is the bright planetary nebula NGC6826.
delta Cygni mags 2.9 and 6.3, sep 2.5”, P.A. 225o (2004)
Slow-moving binary (P ~ 830Y), delta Cyg is a small-scope challenge, due to the difference in the magnitudes of its component stars. Use at least 100X on a night when the seeing is steady.
psi Cygni mags 5.0 and 7.5, sep 2.9”, P.A. 178o (2003)
Like delta Cyg, difficult for small-aperture instruments.
h1470 Cygni mags 7.4 and 9.2, sep 28.6”, P.A. 340o (2002)
I featured this pair in my “Observing Basics” column in the September 2006 issue of Astronomy Magazine. This colorful gold and blue pair is part of a striking arc comprised of four double stars of similar appearance. Find “Chaple’s Arc” by tracing a line from eta Cyg to 25 Cyg and extending it a degree or so beyond.
Omicron1 Cygni mags 3.8, 7.0, and 4.8, seps 107” and 338”, P.A. 328 and 173o (2000)
A wide optical triple, best seen in binoculars and small rich-field scopes. Fine contrast between the golden orange main star and its bluish companions.
61 Cygni mags 5.4 and 6.1, sep 31.1”, P.A. 151o (2004)
This binary pair (P ~ 650Y) is of historical significance as the first star whose distance was accurately determined (Bessel – 1840). Both are orange K-type stars. Dist = 11 LY.
mu Cygni mags 4.8 and 6.2, sep 1.9”, P.A. 312o (2004)
Slow-moving binary pair (P ~ 500Y) that’s gradually closing. The primary star forms a nice binocular pair with a 7th mag star located 200” away.
