Double Star of the Month: Gamma Leonis
AKA: STF 1424, Algieba. Position: 10 hr 20 min +19 deg. 50 min
Due south at 22.46 (GMT) on 15 March 2020.
Image credit: Jeremy Perez (http://www.perezmedia.net/beltofvenus)
Used with permission
Many double stars are attractive because of their colour contrast—Albireo is the classic example—but others are beautiful because of a single colour for both stars. Algieba is such a double star as it has a wonderful golden colour like a lion’s mane which is appropriate for a double located in the “mane” of the constellation Leo. It consists of two bright stars—magnitudes 2.4 and 3.6—with a tight separation of 4.7 which has been widening since it was discovered by William Herschel in September 1782. You will need a high magnification to get a good separation. The orbit of the two stars is about 510 years. The main star is K0 and the secondary is a very similar G7. This means that the main star should be more orange than the secondary but the difference will be very slight and I actually see the secondary as more orange than the primary. Some observers see a greenish tinge. Algieba is easy to find as it is the second brightest star in Leo after Regulus. It is located in the middle of the “sickle” of Leo at the bottom of the “crook” and hence above Regulus. Its orange-yellow colour is obvious even to the naked eye.