Double Star of the Month:
Iota Cancri
AKA: STF 1268. Position: 08 hrs 46 min 41.8 sec 28 degrees 45 min 36 sec
Due south at 21:14 (GMT) on 15 March 2021.
Image credit: Jeremy Perez (http://www.perezmedia.net/beltofvenus)
Used with permission
Because Albireo (Beta Cygni) is so highly regarded, there is great interest in finding a “Winter Albireo”. Such a double star would be yellow and blue and with a fairly wide, but not too wide, separation. We have already met one good candidate 145 (Gould) Canis Majoris (Double Star of the Month for February 2020), but it is rather low in the sky for observers in Havering. This month we look at another well-known “Winter Albireo” namely Iota Cancri. It certainly ticks the right boxes, it is a magnitude 4.1 yellow (G7.5) star and a magnitude 6.0 (A2) star which is a rapid rotator (see the Star of the Month for March 2021) with an easy separation of 30.7 arcseconds. By contrast Albireo is magnitude 3.2 and 4.7 with a separation of 34.6 arcseconds. The two stars in Iota Cancri are physically connected and are a binary system. They are 330 light years away from us. Iota Cancri is also relatively easy to find. It is to the east (or left) of Pollux and forms a roughly equilateral triangle with the bright stars Regulus and Procyon. It is the top left-hand star of the Y-shape formed by the top half of the faint constellation of Cancer, which is roughly halfway between Pollux and Regulus. At magnitude 4 you may need to use the finderscope of your telescope to locate it. William Herschel observed it on 8 February 1782, describing it as red-white and dark garnet (dark red), but it had been observed to be double a few years earlier by the German-Moravian Jesuit astronomer Christian Mayer.