Almach
November 2011 :
Last month, I suggested that our featured object, Albireo, may not be the most beautiful double star in the sky and I’d introduce a rival this month. If you guessed that Albireo’s challenger is Almach, the gamma (?) star in Andromeda, you’d be correct!
The popularity of both Albireo and Almach lies in their stunning golden yellow and deep blue colors. I give Almach a slight edge because its component stars are much closer (slightly less than 10 arc-seconds) than Albireo’s (34 arc-seconds). While Albireo begins to lose some of its visual appeal at high magnifications, Almach is still an impressive sight at powers of 100× and up.
Almach is readily resolved by even the smallest telescopes. Moreover, I found its colors to be more intense when viewed with a 3-inch reflecting telescope than with the 6-inch Clark refractor at the Oak Ridge Observatory in Harvard, Mass.
The latter instrument, however, revealed something the little 3-inch never will. Almach’s fainter component, gamma2 (?2) is a close magnitude 5.1 and 6.3 binary with a period of about 64 years. The two were near their greatest separation (0.6 arc-seconds) when I viewed them with the Clark in 1980. Even then, extremely steady skies and a magnitude of 360× served only to elongate the pair. Right now, the two have closed to a separation of less than 0.1 arc-seconds – a challenge for even the largest telescopes.
We’re not done! The magnitude 5.1 component of gamma2 is a spectroscopic binary with an orbital period of just 2.76 days. Gaze at gamma2, and you’re looking at a tight orbiting triplet!
Both Albireo and Almach are visible on November evenings. You’ve heard my opinion about the two. Now it’s your turn to see for yourself. View both with a variety of magnifications (and telescopes, if possible). Do you agree with my impressions? For a second opinion, read Greg Stone’s comparison of Albireo and Almach on the “Starsplitters” web page at bestdoubles.wordpress.com. Once you’ve accessed the site, enter “Almach and Albireo” in the search box. A quick scroll will get you to his article “Almach: GOLD and blue; Albireo: BLUE and gold – Both: priceless!” By the way, “Starsplitters,” a collaboration of double star fanatics Greg Stone and John Nanson, is a MUST site for the double star enthusiast.
Finder chart for gamma (?) Andromedae (Almach)
From Touring the Universe with Binoculars(TUBA) Star Atlas
Dean Williams and Phil Harrington
