The Bull in the Sky
Exploring Taurus and its environs
In my last stargazing story, we looked at the Winter Hexagon, an asterism of six stars spanning six constellations. Today we’ll take a closer look at two of these constellations, Taurus (the bull) and Auriga (the charioteer).
Taurus is the more interesting of the two. Situated above Orion’s head, it is marked by the orange star Aldeberan and plays host to two naked-eye star clusters. If you have a telescope or even binoculars and reasonably dark skies, you’ll also find the famous Crab Nebula there, the remnant of a bright supernova — a dying star that literally blew itself apart — observed by Chinese astronomers in A.D. 1054.
Let’s start with Aldeberan. Stars, as you probably know, come in a range of sizes from white dwarfs no larger than the Earth to supergiant stars so huge they might fill the orbit of Saturn. Aldeberan is an orange giant that lies 65 light years away. I’m 60 years old now, so the light we now see from Aldeberan left that about star five years before I was born. (Astronomy is time travel!) It has a radius 44 times that of the sun. Its magnitude is about 0.85.
If you don’t remember our discussion of star brightness, here’s the explanation:
Usually the fourteenth brightest star in the night sky, Aldeberan’s brightness varies slightly over time, about two tenths of a magnitude. That’s a small enough variation that you probably won’t notice. To date, we’ve detected one planet orbiting Aldeberan, a gas giant several times the size of Jupiter.
