In the last installment of Naked Eye Astronomy, I concluded with a few questions. It’s time to answer those and continue the exploration of my favorite sky, the winter sky.
Last time, I told you how to find Orion the hunter by looking for his belt and four bight stars, Betelgeuse, Bellatrix, Rigel, and Saiph. You’ll need to find him again because we’re going to use Orion as the starting point to locate some other wonders of the winter sky.
What is Orion Hunting?
You can make a case for just about anything, but I think like Momie Tullottes did in her comment. Orion is hunting Taurus the bull. The fact that Orion is always following Taurus through the heavens gives this story a little validity.
Face south around 11 PM local time and locate Orion’s belt. Follow the line of the belt from left to right (east to west). The first bright orange star you come to is the eye of the bull, Aldebaran (alpha Tau). Aldebaran’s orange glow is streaming across 65 light years to reach us and is still bright at magnitude 0.85. Aldebaran appears so bright after its lights’ long trip to earth because it is nearing the end of its life and has expanded to 44 times the size of our sun.
Can we see any of our relatives up there?
Aldebaran means “follower” in Arabic. Who is Aldebaran following? The seven sisters. Didn’t know you had sisters in the sky, did you? In the lore of the Dakota Sioux, Alderbaran is hunting the white buffalo, but we’ll stick to the Western/Greek lore and call the Pleiades, the seven sisters. If you want to geek your friends out, rattle off the sisters’ names, Sterope, Merope, Electra, Maia, Taygete, Celaeno and Alcyone. Throw in their parents, Atlas and Pleione for good measure. From Aldebaran, just look up the line you traced from Orion’s belt to find the Pleiades. Ever wonder why the car maker Suburu has that funky star symbol? In Japan, the Pleiades are called Suburu.
Where are Orion’s hunting dogs? Where in the winter sky can we find one of our nearest star neighbors?
Orion has two dogs following him on his hunt. They trail just left (east) of him. Go east from the red giant Betelgeuse and the next bright star you’ll find is Procyon, (alpha CMi), the 0.40 magnitude star of Canis Minoris, the little dog. Procyon’s owes its brightness to the relative closeness to our solar system. It’s only about 11 light years away. Now go south, below Orion and about half-way back west to Orion and you’ll find the brightest star in the northern hemisphere, Sirius. Alpha Canus Majoris, is also know as the Dog Star since it is the brightest star of the Big Dog constellation. Sirius appears so bright for two reasons. One, it is about 25 times brighter than our sun. Two, it is one of our closest neighbors at only 8.6 light years.
Sirius has great stories scattered in almost every culture. The ancient Egyptians kept track of Sirius because its heliacal rising coincided with the Nile flood. The Greeks called the month after Sirius’ heliacal rising the Dog Days of Summer because they believed Sirius was adding its heat to the Sun’s to make us all sweat. This also explains why Sirius Radio chose a dog as its logo and why J. K. Rowling named her werewolf character Sirius Black.
So after all these thousands of years, why hasn’t Orion caught that bull?
I blame his dogs. In the right angle, east of Sirius and south of Rigel, is the constellation Lepus. While Orion is trying to catch the bull, his dogs have been distracted by the rabbit under his feet. To the naked eye, Lepus the hare is fairly unremarkable. Arneb (alpha Lep), the brightest star in the constellation went supernova thousands of years ago, probably before there were humans to give the stars names. You can get some idea of what is left of Arneb when you consider the 2.55 magnitude object we see today is 1284 light years away.
I hope that answers the questions I posed last time. There is plenty more to explore in this part of the sky. Next time well talk about chauffeurs, twins, and unicorns.