The sky is divided into 88 official constellations. In fact, though, it’s more like 88 and a half. That’s because the constellation Serpens consists of two disconnected parts – a head and a tail. They wrap “behind” the body of Ophiuchus the serpent bearer.

Serpens is in full view in the east and southeast by a couple of hours after sunset. The half that represents the head is highest, above Ophiuchus, with the tail below the serpent bearer.

The front of the snake, Serpens Caput, is the more prominent half. It has several stars that are fairly easy to see. The brightest is Alpha Serpentis, also known as Unukalhai – “the serpent’s neck.” It’s a red giant – an old, bloated star that’s much bigger and brighter than the Sun. Its surface is much cooler than the Sun’s, so the star looks yellow-orange.

The back half of the snake, Serpens Cauda, is tougher to spot. Its brightest star, Eta Serpentis, is the second-brightest star in the whole constellation. It’s about half as bright as Alpha. But the two stars are quite similar. Eta is also a giant – a puffed-up star that’s nearing the end of its life. It’s a little farther along than Alpha, so it’s a little bigger and brighter. It looks fainter because it’s farther away.

The two stars will end their lives in the same way. Each will cast its outer layers into space, leaving behind a hot but tiny corpse known as a white dwarf.

More about Serpens tomorrow.

Script by Damond Benningfield