“V” may be for victory, but it’s also the shape of one of the closest star clusters to Earth: the Hyades (HYE-uh-deez). That distinctive shape that makes finding this star cluster easy peasy on a November night. You may already be familiar with the Dipper-shaped Pleiades cluster also known as the Seven Sisters. This pretty bunch has been climbing the eastern sky all fall and is now conveniently placed for viewing around 9 o’clock. Make a fist at the sisters and then look one fist below them. The first star to catch your eye will be a bright orangish spark called Aldebaran (al-DEB-are-on). Spreading to the right of the star are the fainter Hyades. From our perspective on Earth, the cluster appears like the letter “V”, but its true shape is approximately spherical. At first glance, you’ll nail a half-dozen stars with your naked eye, but in total the Hyades contains some 300-400 stars 151 light years from Earth. It’s one of the closest star clusters to our solar system; the Pleiades in contrast is three times farther or about 400 light years away.
Beware Aldebaran! It seems to fit the V to a tee, but like someone sneaking into a wedding party who doesn’t belong, Aldebaran has no association with the cluster. It’s in the foreground 65 light years from Earth, and coincidentally happens to be in the same line of sight as the Hyades. Without Aldebaran, the cluster would be a little disappointing; the star adds luster and helps shore up the overall shape.
Once you’ve found the Hyades, try to split the close naked-eye double star Theta Tauri, just to the right of Aldebaran. Astronomers aren’t sure it’s a true double star, but both belong to the cluster. Although separated by slightly less than a 1/10 of a degree, I can split them fairly easily when staring squarely at the pair. Another challenge is to see how many Hyades are visible from where you observe. At my house, on a dark, moonless night, I count a dozen stars within or very close to the V-shaped outline. A few additional members lie scattered about outside the V. How many do you see? The best way to find the faintest ones is to use averted or peripheral vision. Look off to this side or that rather than staring directly at the stars.Â After you’re finished with the Hyades, try the same technique with the Pleiades. With a little concentration, I bet you’ll see several more than the usual five most folks see at a casual glance. Little exercises like these sharpen our perception and sometimes surprise us. I never thought I’d see the zodiacal light or its ghostly cousin, the gegenschein, but once I tried and learned to know what to look for, they’re visible many clear nights.
The Hyades has been hanging together a long, long time. Astronomers estimate its age at 625 million years. Many star clusters don’t make it beyond 100 million years, especially those with only a modest number of stars or located closer in to the center of the Milky Way galaxy. Over 1100 star clusters like the Hyades are known in our galaxy (there are likely many more remaining to be discovered), and most “evaporate” or break apart into individual stars over time.
As star clusters revolve around the galaxy’s center, members leave the cluster through gravitational interactions with one another as well as chance encounters with other stars and interstellar gas clouds (and their gravitational meat hooks) met along the way. The Hyades have held together for ages, because they’re out along the edge of the galaxy, opposite the center and thousands of light years away from the heavy stellar traffic of the interior regions. The cluster may also have been blessed at birth with a bigger brood of stars than most. More stars means you’ve got the gravitational wherewithal to keep yourself intact longer. Even if you lose a few, you’ve got more where those came from. Whatever the detailed history of the Hyades, they’ve emerged victorious after 625 million years, and we’re here to celebrate their twinkling place among the stars of November.