Double Star of the Month - January 2010
In this series of short articles, a double star in both the northern and southern hemispheres will be highlighted for observation with small telescopes, with new objects being selected for each month.
Lying about 4 degrees following iota Aur, the fainter of the stars in the horns of Taurus, is 14 Aurigae = STF 653 (05 15 24.39 +32 41 15.3) a bright and easy pair (magnitudes 5.01 and 7.33) currently separated by 9".8. Good nights in small telescopes may also reveal the fainter (11.0) component C at a similar distance and first seen by F G W Struve, although Sissy Haas did not see it in 12.5-cm. Lewis in his work on the Struve stars (1906) lists a number of colour estimates for the two components - Dawes: yellow and blue, Smyth: pale yellow and orange, Dembowski: yellow and blue, Duner: yellow and azure, and Perrotin: white and orange. More recently, Haas notes it as bright straw yellow and royal blue. The system as a whole is a complex one. A is also a spectroscopic binary and a delta Scuti variable known as KW Aur. C is thought to be physical, whilst B merely reflects the proper motion of A. However, C itself is a spectroscopic binary and HST observations have recently established the presence of a white dwarf companion (Cb) 2" away whose connection to Ca has not been established. 14 Aur A lies at a distance of 286 light years.
kappa Leporis (05 13 13.88 -12 56 28.7), whilst certainly in the southern hemisphere, tantalizes the northern observer as the constellation below the feet of Orion can be seen briefly as Orion culminates. Many of the doubles noted in Lepus by Webb are unequal and this pair is no exception - A and B are respectively 4.43 and 6.99 according to Makarov and Fabricius in their analysis of Tycho-2 magnitudes) but also the relative close separation (now just under 2", having been closing since discovery in 1832). The writer has measured it with 20-cm but the seeing more than 60 degrees from the zenith is rarely good. Hartung reports that it easy with 7.5-cm from Australia. The primary is a late B dwarf but Smyth recorded pale white and clear grey for 1835 whilst Webb notes colours of yellow and grey in 1851.
Bob Argyle - Double Star Section Director