A Selection of Double Stars in Corona Borealis
April 2007 :
It’s time to come out of hibernation! After two months of intense cold weather here in the Northeast, mild temperatures are returning. Celebrate spring with a visit to one of the season’s loveliest constellations, Corona Borealis. The Northern Crown is home to a splendid collection of double stars. Here are ten of the most noteworthy.
Struve 1932 CrB magnitudes 7.3 and 7.4, separation 1.6 arcseconds
Neat pair of yellowish twins, located one-third of the way between alpha Coronae Borealis and epsilon Bootis. Use 100X or more for a clean split.
eta CrB (Struve 1937) mags 5.6 and 6.0, sep 0.5”
Fast-moving binary pair with a period of 41.6 years. Requires at least an 8-inch scope, high magnification (200-300X), and optimum seeing conditions.
Struve 1964 mags 7.9 and 8.1, sep 15.3”
Faint, but pretty, duo situated in the same low-power field as zeta CrB (see below).
zeta CrB (Struve 1965) mags 5.0 and 5.9, 6.3”
A beauty! Components seem white to bluish.
gamma CrB (Struve 1967) mags 4.0 and 5.6, sep 0.7”
Like eta CrB, a close binary (P = 91 years) that requires high magnification and steady skies. A challenge for a 6-inch telescope.
Struve 1973 CrB mags 7.6 and 8.8, sep 30.5”
To find this relatively faint pair, scan an area slightly north of a point midway between kappa and zeta CrB.
Otto Struve 302 CrB mags 7.2 and 10.4, sep 29.1”
In small-aperture scopes, you may need averted vision to pick out the faint companion. You’ll find this double midway between rho and Kappa CrB.
sigma CrB (Struve 2032) mags 5.6 and 6.5, sep 7.0”
Like zeta CrB, a showpiece double. This very slow-moving binary (P ~ 1000 years) sports colors that appear somewhat yellowish.
nu CrB (Struve I 29) mags 5.4 and 5.6, sep 360.8”
Very wide - best seen in binoculars or low-power rich-field telescope. Component stars seem decidedly yellowish.
H V 38 CrB mags 6.4 and 9.8, sep 31.7”
Plotted on some atlases as 23 Herculis (the home constellation for this star before the IAU redefined constellation boundaries in the 1930’s), this pair is located a little over a degree south of nu CrB.
