Double Star of the Month - January 2012

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.

35 Cam (06 04 29.10 +51 34 24.2) was observed by Madler in 1843, and became number 128 in the Pulkovo Catalogue of Otto Struve, although it had been discovered by John Herschel in 1830. Later authorities including Aitken in the ADS added the word rejected because the separation was too wide for the pair to be a likely binary system. The rejected tag seems to have been removed in the current WDS but there is no evidence that the two bright stars are connected. The pair is a fine sight in a small telescope - the primary appears white and V = 6.4, whilst a V = 9.26 mag. bluish companion sits about 40 arc seconds away in PA 14°. For the user with say 30-cm there is the additional interest that the companion is a close pair - HU 559 which appears to be moving in retrograde binary motion - some 30 degrees since the discovery by Hussey in 1902. The WDS gives magnitudes of 9.6 and 10.6 and the current separation is 0".6 so this is as much of a test of the atmosphere as it is of the telescope.

The constellation of Columba lies to the south of Canis Major and a triple star worth seeking out is HJ 3858 (06 25 30.01 -35 03 50.5). It forms an isosceles triangle with kappa and delta Col and is exactly 5 degrees south of zeta CMa. This is both an easy binocular pair and a fine triple in the small telescope. The brightest stars have magnitudes 6.4 and 7.6 and are separated by 131" a distance which is slowly increasing. The primary star, of spectral type K3 appears deep yellow to Gould with 175-mm, whilst the companion appears white, reflecting its spectral type of A4. When John Herschel noted it on sweep 663 at Feldhausen, he described its three stars as 'Fine object. A star 6 mag precedes to the south'. The close pair (BC) is currently 3".8 apart and also slowly separating with little change in position angle, and the magnitude of C is 8.2.

Bob Argyle - Double Star Section Director