There are two main kinds of star clusters in the sky — globular clusters and open clusters. Globular clusters, such as the Hercules cluster, are densely packed, nearly spherical balls of stars, typically seen in the distant halo of the Milky Way. Open star clusters are much smaller, younger, are embedded within the spiral arms of the galaxy, and don’t have a clearly defined shape. When people think of open star clusters, the first thing that typically springs to mind is the Pleaides, the well-known seven sisters seen in the shoulder of Taurus the bull. While these stars are an astronomical delight, an oft-overlooked open cluster is right next door.

Look for the red giant star Aldebaran and then notice the V-shaped group of stars making up the head of the bull. A quick trick to find it is to follow the three belt stars of Orion west in the sky. This cluster, known as the Hyades, is actually closer to us and takes up a larger portion of the sky than the Pleaides.

Aldebaran seems to be the brightest of the Hyades, but this is a line-of-sight illusion. Aldebaran is a mere 65 light-years distant, while the Hyades is more than 150 light-years away (compared to the Pleaides at nearly 450 light-years). Observing the cluster reveals hundreds of stars, all thought to have formed from the same cloud of gas some 600 million years ago. As clusters like this orbit the galaxy, they tend to split apart in a process known as evaporation, and within a billion years the cluster will have become distributed among the rest of the Milky Way stars.

First Published: February 4, 2020, 1:00 p.m.