A Selection of Double Stars in Scorpius
July 2007 :
Our summer double star adventure takes us to the southern skies and the constellation Scorpius. The region north and west of, and including, Antares contains a remarkable array of showpiece double and multiple stars. Data on magnitudes and separation were taken from the Washington Double Star Catalog.
Omega 1,2 Scorpii mags 4.0 and 4.3, sep 15 arcminutes
While waiting for your telescope to cool down, look for the naked eye pair omega 1,2 Scorpii, situated a degree south of beta Scorpii. These fourth-magnitude stars, about as far apart as the Mizar-Alcor pair in Ursa Major, are a nice sight in binoculars.
Beta Scorpii mags 2.6 and 4.5, sep 13.6”
One of my favorite double stars, beta is an easy split in a common 60mm refractor. Nice contrast between the white primary and its companion, which appears blue to blue-green.
Xi Scorpii magnitudes 4.9 and 7.3, separation 7.5 arcseconds
Struve 1999 Scorpii mags 7.5 and 8.0, sep 11.8”
This is a beautiful “double-double” for small scopes. Separated by just 5 minutes of arc, the two pairs are a dazzling sight at 60X. The primary to xi Scorpii is a close binary with a 45.7 year orbital period. Current separation from the mag 5.2 companion is about one arcsecond, so you’ll need a large telescope, optimum seeing, and a magnifying power of 200X or more.
Nu Scorpii mags 4.2 and 6.6, sep 40.8”
Small-scope owners using 50X will see a wide pair, but wait! If the seeing is good and you “jack up” the power to 120X, you’ll spot a 7.2 magnitude star just 2.4” from the fainter component. The 4.2 mag primary isn’t alone, but you’ll need a 6-inch scope and 150X to bridge the 1.2” gap separating it from its 5.3-mag partner.
Sh 225 Scorpii mags 7.4 and 8,1, sep 46.9”
Sh 226 Scorpii mags 7.6 and 8.3, sep 12.8”
This little-known “double-double” was brought to my attention by the Mexican amateur astronomer Juan G. Hernandez back in the days when I wrote a double star column for Deep Sky Monthly. To find these two pairs, look 3 degrees north of the globular cluster M80.
Sigma Scorpii mags 2.9 and 8.4, sep 20.0”
Easily found just 2 degrees east and slightly north of Antares, this pretty duo is well-seen in small scopes at 50-75X. Try averted vision if the 8th mag companion proves elusive.
Alpha Scorpii (Antares) mags 1.0 and 5.4, sep 2.5”
Our final double star offers a stern challenge, due to its closeness and the difference in magnitude between its component stars. Though not as difficult as Sirius, Antares will require a good 6-inch scope and near-perfect seeing conditions. Most observers report a striking color contrast between the ruddy primary and its greenish companion
