Now that the eclipse is behind us, the moon has trotted off to the east out of the limelight.
It’s in that lengthly phase called waning gibbous, a period of 6+ days between full moon and last quarter. Can I coax you out for another look?
Tonight the moon will cross the Hyades star cluster that forms the V-shaped face of Taurus the Bull. Merely having the moon in Taurus hints at how close we are to the start of winter. Two months hence, the Bull, along with Orion the Hunter, will dominate the southern sky at 10 o’clock.
But tonight around 10, Taurus makes its appearance in the eastern sky. Because the moon is still fat and bright you’ll better appreciate its passage through the Hyades with binoculars. By happy circumstance, the entire cluster neatly fits into the field of view of most pairs.
Orange-red Aldebaran is Taurus’ brightest star and completes the cluster’s V with a flourish. Don’t be deceived. This star is an impostor that by chance lies in the same line of sight as the star cluster. The Hyades form a gravitationally bound group of stars 153 light years distant and were born from the same cloud of gas and dust 625 million years ago. Aldebaran? Only 65 light years away and as solitary as our sun.
Over the course of the night, the moon will slowly work its way across the Bull’s face, occulting or covering a number of fainter cluster stars along the way. One such star is 63 Tauri shining at magnitude +5.6. A small telescope 4-inches or larger will show the moon creep up to the star and suddenly blank it from view around 10:10 p.m. Central Daylight Time. Depending on your location, the moon’s path across the Hyades will shift a little north or south, and you may see different stars occulted.
By 5 a.m. CDT tomorrow morning Oct. 12 the moon will be in conjunction with Aldebaran about 1º to its north. Here we see yet another of nature’s illusions. The moon not only outshines Aldebaran by 26,000 times, it’s huge in comparison. But make no mistake, Aldebaran’s the giant here. Next to it, the sun looks puny and faint.
With a diameter 44 times solar, Aldebaran’s searing orange photosphere would reach all the way to the planet Mercury if put in place of the sun and overall shine 500 times as bright.
Another noteworthy star to look for in your binoculars is the pair called Theta 1,2 Tauri. Both belong to the Hyades although small uncertainties in their distances make it unclear if they’re a physical double star or like Aldebaran, a chance alignment. Once the moon’s out of the way, this is a fun star to try and split with your naked eye. Like two tiny pearls in a starry brooch, they make for a pleasing sight.