Jimmy Westlake's Celestial News column appears monthly in the Steamboat Today.
Find more columns by Westlake here.
“Beautiful” isn’t a word one usually uses to describe the face of a bull, but Taurus, the celestial bull, is an exception. The familiar V-shaped asterism of Taurus’ face hanging high in our winter sky is like no other group of stars visible from Earth.
Collectively known as the Hyades, the stars that outline Taurus’ face are all members of a single star cluster, born together as one family — with one notable exception. The brightest star in this “flying wedge,” as I used to call it as a kid, is Aldebaran, an orange giant star marking the glaring eye of the heavenly bull. Aldebaran is a foreground star, only half as far away as the Hyades and conveniently positioned atop the “V’s” left fork. Unlike the nearby Seven Sisters star cluster that has only a half dozen or so naked-eye stars, the Hyades boasts at least a dozen members visible to a good eye on a dark night. What the human eye alone cannot see are the hundreds of fainter cluster members lurking just below naked-eye visibility.
The Hyades cluster, 153 light-years away, has the distinction of being the closest star cluster to our solar system. Astronomers hone their distance-measuring skills on the nearby Hyades cluster in order to better measure the distances to other stellar clusters much farther away.
The brightest Hyades outlining the bull’s face are all orange giant stars. Born about 625 million years ago, these stars already have fused up their hydrogen fuel and are entering their final stage of life, cooling and swelling at the same time into orange behemoths that would dwarf our sun. Hyades stars more massive than these few have already run their course and blown themselves to smithereens.
Astronomers have uncovered evidence that our sun was born with dozens or hundreds of siblings in a Hyades-like star cluster some 4.6 billion years ago. Star clusters generally don’t survive that long because the stars are stripped away and leave their nest after about a billion years. Still, the ancient M67 star cluster in Cancer the Crab shares many common traits with our sun and seems a likely place of birth.
Blazing brightly beside the face of the bull this winter is the giant planet Jupiter. Look for Aldebaran, the Hyades and dazzling Jupiter high overhead as darkness falls this month.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. Check out his astrophotography website at www.jwestlake.com.