Double Star of the Month:
12 Lyncis
AKA: STF 948
Position: 06 hr 46.2 min +59 degrees 26 min 30 sec
Due south at 23:08 (GMT) on 15 January 2022
Image credit: Jeremy Perez (http://www.perezmedia.net/beltofvenus)
Used with permission
Lynx is an obscure constellation between Ursa Major and Gemini. It is a long line of 19 faint stars which was given the name Lynx by the astronomer Johannes Hevelius in 1687 on the grounds that you need to be lynx-eyed to make it out. However it does contain a decent number of doubles, two of which have been moved into Ursa Major. 12 Lyncis is one of the best of these doubles; to be more precise it is a triple. The star has a magnitude of 4.9, so you will probably not see it with the naked eye in Havering. The main star has a magnitude of 5.4 and its closest companion is magnitude 6.0. The separation is a rather tight 1.9 arcseconds, but the similarity in brightness will help you to split it at high magnification. The third member is magnitude 7.0 and is 8.9 arcseconds distant, roughly at a right angle to AB. The stars are a few light years from each other, but they do form a physical system which is approximately 240 light years distant from us.
All three are hot massive A type stars and C may be somewhat younger than the other two. Hence one would assume that they would all be white, but they are usually seen as yellow, yellow and light blue. Herschel observed it on 7 August 1780 “somewhat under the eye of the Lynx” and called the first two stars pretty unequal; which seems surprising as he describes the difference between B and C with almost twice the magnitude difference as pretty unequal as well. He described the colours as white, white inclining to rose and the third as pale red.
It is not an easy star to find. Take the two stars at the top of the bowl of the Plough – Megrez and Dubhe – and draw a line to the bright star Capella. 12 Lyncis lies on this line forming a triangle with the brighter 15 Lyncis (mag. 4.4) and the dimmer 14 Lyncis (mag. 6.0); 12 Lyncis being the leftmost or westernmost of these stars. It is also roughly half-way between Muscida (Omicron Ursa Majoris, mag. 3.4) and Capella.