Spring Double Stars: The Three Leaps of the Gazelle
March 1997 :
The Great Bear Ursa Major is high in the northwest these late Spring evenings. Along his southwestern border, shared with the constellations Lynx, Leo Minor, and Leo lie the three distinctive pairs of third magnitude stars known from ancient times by many names, one of the best known of which is the charming name "The Three Leaps of the Gazelle." Three of the six leap stars are wonderful doubles, and there are many more awaiting discovery in Ursa Major.
? (xi) UMa
This star is the "bottom" star of the southernmost leap, and is a fine close binary system for modest-sized scopes. The golden stars are magnitudes4.5 and 5.0 and are separated by 3 arcseconds; a lovely pair at 150 power.
? (nu) UMa
The "top" star of the bottom leap pair of stars and a very different double from its neighbor xi. The components of nu are magnitudes 3.8 and 10.0, separated by 7 arcseconds. The bright primary accompanied by its faint speck of a companion, is a striking sight at 150 power.
? (iota) UMa
The "top" star of the northernmost leap. This double is listed as magnitude 3.1 and 9.5, separated by 4 arcseconds. I have tried a number of times to split this with my 6 inch f/8 Dobsonian and have not been able to do it on nights when the scope has split zeta Bootis, a pair of 5th magnitude stars only 1 arcsecond apart. Fairly close pairs like iota with large magnitude differences between the components are more difficult to separate than stars whose magnitudes are of like magnitudes. I'd enjoy hearing from anyone who has observed this double star.
65 UMa
A neat triple of white stars about 5 degrees due south of gamma UMa. At 45x, the star is a pleasant pair of matched white magnitude 6.5 stars. At higher powers one of the pair resolves into a magnitude 6.5 and 8.5 pair separated by 3.5 arcseconds. Of this latter pair, Burnham's Celestial Handbook says that the brighter star itself is a double star whose components are a mere 0.3 arcseconds apart, making 65 UMa actually a quadruple star!
?2 (sigma 2) UMa
Visible to the naked eye at magnitude 4.5 under reasonably dark skies, and a fine system. This double's stars are magnitude 5.0 and 8.5, 2.5 arcseconds apart. Looks good at 200 power. Sigma 2 has another companion of magnitude 9 about 200 arcseconds distant.
23 UMa
This easy triple system's A and B components of magnitudes 4 and 9 are 22 arcseconds apart; the magnitude difference is enjoyable. 100 arcseconds from the A star is the magnitude 10.5 C star.
It's always nice to end such an observing evening with Mizar and Alcor in the Dipper's handle.
