Thursday, June 27, 2013

The cat's eyes in the Scorpion

This is a beautiful time of year for observing the constellation Scorpio, who is easily seen rising up from the horizon in the hours after sunset.  

Scorpio is a like gleaming string of jewels in the southern sky (for northern hemisphere viewers), with brilliant red Antares at his heart -- the constellation's brightest and most distinctive star and the largest in the chart above (marked by the Greek letter lower-case alpha, and the word "Antares").  Currently, Antares reaches its highest point on its arc at about 11 pm, and then reaches it about four minutes earlier each night as the earth continues its orbit around the sun (for more on that process, see the discussion in this previous post and the video in this one).

If you can observe Scorpio around that point of its highest elevation (also known more precisely as its transit across the meridian) or in the hours after that -- for instance, around midnight -- you will have an opportunity to see the charming pair of stars near the end of its stinger-tail, a pair of stars known as "the cat's eyes."  As Scorpio begins to arc back down towards the western horizon, the cat's eyes become nearly horizontal, and they really do look like a pair of cat's eyes, gleaming out at you in the night sky!

The cat's eyes are pointed out by the two arrows in the above chart.  They are a bit further apart in the night sky -- the chart makes them look as though they overlap, because it depicts each star as larger or smaller depending upon its brightness, and the "eye" on the left is a bit brighter than the other, so its depicted size is larger on the chart than it looks when you go out into the night.  In actual fact, they are about as far apart as . . . the eyes of a cat!

In his superlative book for star-gazers, The Stars: a New Way to See Them, author H.A. Rey writes: "Look for the CAT'S EYES, a close pair of stars in the Scorpion's tail.  You will find the name quite fitting" (52).  They are especially easy to spot on nights like tonight (and the next several nights) when the moon does not begin to rise in the east until nearly midnight, and getting later and later each night as it wanes.

Once you have located the cat's eyes, you will want to look for them again and again!  

For previous posts discussing Scorpio and how to find that constellation, see here and here.  For a previous post with an image of cat's eyes, see here.