Wednesday, June 12, 2024

Double Stars in Hercules (all night)

Hercules contains double and binary stars that are within reach of a backyard telescope, even when the moon is around. One of the nicest is modest Rasalgethi, or Ras Algethi 'Head of the Kneeler', which sits about 16 degrees to the southwest of the bottommost corner of the keystone (close to the boundary with Ophiuchus). In a small telescope, Rasalgethi easily splits into a lovely pair of orange and greenish stars. The slightly brighter one is a red giant class star that varies in brightness randomly over months to years. The partner is a yellow Sun-like star that is itself a binary star too tightly spaced to resolve. The stars are about 360 light-years away and are orbiting one another with a period of 3,600 years. This double star, like many others, was given a single name centuries before telescopes revealed that there was more than one star there. Gamma (Y) Herculaneum, sometimes called Nasak Shamiya III is another pair that easily splits into two yellow stars in a modest telescope. Marsic 'the Elbow', aka Kappa (K) Herculaneum, is another easy 'line of sight' double star.

(Data courtesy of Starry Night)
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* Origin: CJ's Place, Orange City FL > cjsplace.thruhere.net (21:2/156)