As pointed out in previous installments of this column, the stars of each of the four seasons are arranged in characteristic geometric patterns that make identifying them easy and fun. Here this month in late winter we find the most striking of them—the famed “Winter Circlet” asterism. It fills the evening sky after darkness falls with the greatest concentration of bright colorful stars to be found anywhere!
To trace out this asterism, begin by setting your Scientifics Star and Planet Locator for around 8 p.m. local time at the beginning of March when the Circlet is centered on the celestial meridian—the imaginary north-south line in the sky passing directly overhead. (Note that it moves to the southwest as the evening becomes later and the month progresses). Facing south, you’ll be immediately dazzled by the radiant constellation Orion the Hunter standing astride the meridian.
Directly high above Orion is the lovely golden sun Capella in the pentagon-shaped constellation Auriga the Charioteer. Proceeding counterclockwise, we come to the bluish-white star Castor and its slightly orange neighbor Pollux, both in the figure of Gemini the Twins. Continuing southward is yellowish-white Procyon in Canis Minor, the Small Dog, and below it the brightest star in the entire heavens — the dazzling blue-white diamond Sirius in Canis Major the Big Dog. Heading westward we next encounter another bright blue-white gem, Rigel in Orion. We complete the circle by heading northwest to the upper right of Orion, where we find orange Aldebaran set against the sparkling V-shaped glow of the big Hyades star cluster in Taurus. Finally, at the center of the Circlet itself we find the magnificent ruddy supersun Betelgeuse in Orion.
This asterism is also sometimes referred to as the “Heavenly-G” with the circle breaking inward to Betelgeuse to form that letter in the sky. Others fancifully see here instead a celestial campfire. Completing this particular celestial imagery appearing like some great glowing ember in the sky is Betelgeuse. So fire-like is this star in appearance that looking at it definitely does bring a feeling of warmth, real or not!
In pointing out the hues of the various stars above, it should be mentioned that differences in their colors is primarily an indication of differences in temperature (not composition, as many believe). Hot stars are bluish-white and cool ones are ruddy, while those in between in temperature (like our own Sun) are yellow or orange. And yes, there are even a few greenish stars but not among the brighter ones. Thus, it’s actually possible to tell something of the physical nature of other stars simply by looking at them! As one star lover more than a century ago stated, “Every tint that blooms in the flowers of Summer flames out in the stars at night.”
Note that you can find additional information about seven of the eight stars discussed above, including their distances, on the reverse side of the Star and Planet Locator. The one exception is Castor, which lies 52 light-years from us. It’s officially just below the cutoff for being a “first-magnitude” star even though it is often included in that select group by sky-watchers.
— James Mullaney
Former assistant editor at Sky & Telescope magazine & author of nine books on stargazing. His latest, Celebrating the Universe!, is available from HayHouse.com.