Pegasus, the flying horse, is climbing across the night sky. It’s in the east as night falls. It’s preceded by another horse, which is to the upper right of Pegasus.

Equuleus is far smaller and less prominent than its equine cousin. In fact, of all the constellations passed down from the ancient world, it’s by far the smallest — you can cover it with your palm held at arm’s length.

Unlike most ancient constellations, there’s not much of a story associated with Equuleus. And as it’s drawn in the sky, it’s not even a full horse — only a head, which is outlined by a lopsided rectangle of four meager stars.

The brightest of the four is Alpha Equulei, which actually is a pair of stars locked in a tight orbit around each other. Both stars are about twice as massive as the Sun, with one slightly heavier than the other.

The difference in heft has made a big difference in the lives of the two stars. The heavier one has already ended its “normal” lifetime, and is entering one of its final stages. That’s caused the star to puff up like a balloon.

The smaller star is still in the prime of life. Yet as the bigger star puffs up, the surfaces of the two stars may get so close that the stars will swap some of their gases — altering the evolution of both stars.

Equuleus is in the southeast at nightfall. It’s below Delphinus, the dolphin — another small constellation, but one that’s much easier to pick out.
 

Script by Damond Benningfield

Support McDonald Observatory