Star of the month
Alkalurops (Mu (m) Bootis) is located close to the eastern border of Boötes, just to the northeast of the Kite asterism which represents the main body of Boötes the Herdsman. The name Alkalurops means ‘a herdsman’s staff’ or ‘ club’.
As with many of the stars which appear as single objects, under close scrutiny Alkalurops isn’t alone but rather a pair of double stars which may or may not be physically connected. The two pairs are designated Mu-1 ( m1) and Mu-2 ( m2) Bootis. The Mu-1 pair to the west carry the official name Alkalurops and appear close as seen from Earth with a narrow separation of 0.08 arcseconds, too close to be separated by amateur equipment. To us the primary appears as a F0 V star of mag. +4.3. This spectral type indicates a yellow-white colour and a main sequence dwarf-type star. Having a close physical separation, the orbital period of Mu-1 is rapid, estimated to be in the order of 300 days. The pair are referred to as Alkalurops Aa.
The Mu-2 pair can be split using amateur kit, having an apparent separation of
2.2 arcseconds. Designated as Alkalurops BC, their colours are distinctly more yellow than Mu-1. Their individual spectral types are of G1V (the brighter component) and G5V, the
‘V’ indicating that they are main-sequence dwarf stars. Their individual magnitudes are +6.5 and +7.8 and their orbital periods are significantly longer than Aa, that for BC being estimated at 260 years. The two pairs are separated by 108 arcseconds making it possible to see the Mu-1 and Mu-2 pairs in the same field of view. A magnification of x250 will confidently split the Mu-2 pair.