We owe our ancient stargazing ancestors a great deal when it comes to stargazing. For example, Greek astronomers identified a number of objects that we can still find with the naked eye (provided the light pollution isn't too bad). For example, the Pleiades star cluster is a relatively easy one to spot in December's skies.

Not far from the Pleiades is another one the Greeks spotted and told tales about: the Hyades star cluster.


These stars represent the daughters of the Greek Titan named Atlas. They were half-sisters to the Pleiades (who were also daughters of Atlas by another mother). The Greeks weren't the first to tell tales about this star cluster, but it often seems to be associated with rain. 

In reality, the Hyades are more closely related to another star cluster called "Praesepe", or the Beehive, which is an early spring object for Northern Hemisphere observers. Astronomers have long suspected that these two clusters had a common origin in an ancient cloud of gas and dust. The Hyades stars lie about 150 light-years away from us, and formed some 625 million years ago. They travel together through space in the same direction. Eventually, even though they do have a slight gravitational attraction for each other, they will go their separate ways, just as the Pleiades will do. At that point, even though their stars may have "unlinked" from the cluster, they're still traveling along the original trajectory.

Astronomers call them "moving group" or a "moving cluster". 

There are about 400 stars in the Hyades, but we only see about 6 or 7 with the naked eye. The four brightest Hyades stars are red giants that formed as massive A-type giants. They've run through their nuclear fuel and are heading toward old age and eventual destruction. These stars are part of the V shape that ancient skygazers thought made up the face of a celestial bull named Taurus. 

The brightest star in the Hyades really isn't in the Hyades. It's called Aldebaran, and it happens to lie on the line of sight between us and the Hyades. It's an orange-hued giant that lies only 65 light-years away. Aldebaran is an old star that will eventually exhaust all its fuels and could eventually explode as a supernova before collapsing to form a neutron star or a black hole. Unlike Betelgeuse (the supergiant star in Orion's shoulder, which could explode anytime as a supernova), Aldebaran will likely be around for millions of years.

Both the Hyades and Pleiades are open clusters -- that is, they are associations of stars that are born in the same clouds of gas and dust, but are not tightly bound together by gravity as stars in globular clusters do. The Milky Way contains at least a thousand of these collections of stars and astronomers study them to understand how stars of similar ages evolve over time. From the time they form together in their birth clouds to the time they die, star cluster members show us how stars of roughly the same age, but different masses, can change over time.

The highest-mass ones will use up their nuclear fuel very fast and die after a few hundreds of millions of years. Those same stars use up tremendous amounts of the original cloud as they form, which reduces the supply of star-making material available to their sibling stars. So, like the Hyades, many open star clusters contain members that are the same age, but some look older than others (thus illustrating the old adage, "live fast, die young, leave a beautiful body").