Tonight, March 27, the waxing moon is high in the southern sky, shining in the center of the bright Winter Circle of stars. The Winter Circle is an asterism – a distinctive pattern of stars that is not a constellation.
The easiest way to find the Winter Circle is to locate the constellation of Orion the Hunter, identified by his belt of three bright stars in a straight line. In this season Orion, as Robert Frost wrote, rises sideways. Rigel is the bright star at the Hunter’s foot.
Orion’s belt points down directly to Sirius, popularly known as the Dog Star. The belt points in the other direction to red star Aldebaran. Moving clockwise on the left-hand side of the circle, Procyon is above and a little to the left of Sirius. Continuing clockwise around the circle, twins Castor and Pollux are above and a little to the right of Procyon. And at the top of the circle is bright Capella, in reality a double star.
Within the circle and at its center is red Betelgeuse, at the Hunter’s shoulder. Also known as the Winter Hexagon, the Winter Circle is very large in extent, covering almost a third of the dome of the night sky. Because Orion lies on the celestial equator, the Winter Circle can be seen from all locations on the globe, except very southerly latitudes. In the Southern Hemisphere it is called the Summer Circle and includes the star Canopus.
Also bright in the night sky is Jupiter, a little to the left of the Winter Circle. Planets can be easily distinguished from stars because they shine steadily, while stars twinkle. And finally, in case your life keeps you out very late at night, or very early in the morning, remember to look up at the sky for the Milky Way. It is best seen in summer, but is visible now as a stream of heavenly light, even in areas with high light pollution.
Speaking of light pollution, Saturday March 28 at 8:30 pm local time is International Earth Hour, observed around the world. To participate, simply turn off all nonessential lights for one hour. And 2015 is the International Year of Light, also to support energy conservation and reduce CO2 production.
