by Geoff Chester, USNO Public Affairs | 20 February 2024 The Full Moon, imaged 2023 March 7, 01:59 UT from Alexandria, Virginia with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor, Antares 1.6X 2-inch Barlow lens, and a ZWO ASI183MC CMOS imager. The Moon waxes to her full phase this week, brightening the sky around spring’s rising constellations. Full Moon occurs on the 24th at 7:30 am Eastern Standard Time. February’s Full Moon is popularly known as the Snow Moon, an appropriate name for winter’s snowiest month. Native Americans called it the Hunger Moon due to the scarcity of food, or the Bear Moon since this is the time of year when bear cubs are born. Luna starts the week near the bright star Pollux in the constellation of Gemini. On the 23rd she may be found about three degrees north of the star Regulus, the “heart” of Leo, the Lion. The bright Moon washes out many of the fainter stars that “flesh out” many of the constellations, but the stars of the Great Winter Circle continue to shine brightly despite Luna’s scattered light. The central figure in the Circle is the distinctive form of Orion, the Hunter. His most striking feature are the three blue-tinted stars that form his “belt”. Using these stars as a starting point, we can follow a clockwise arc around the Circle’s bright periphery. Draw an imaginary line through the belt stars toward the southeast. There you will find Sirius, the brightest star in the night. Sirius is located a mere 8.5 light years from the Sun, and is about 25 times more luminous than Old Sol. It is a binary star system, with the bright component accompanied by a faint white dwarf. If you happen to be 8.5 years old, the light we see from Sirius tonight began its journey toward us when you were born. We can look at the other bright stars of the Circle as “birthday stars”. North of Sirius is Procyon, the eight-brightest star in the sky. It is about seven times as luminous as the Sun, and is located 11.5 light years away. Like Sirius, Procyon also has a faint white dwarf companion. Next in line as we curve northwest are the twin stars of Gemini, Castor and Pollux. Pollux is somewhat brighter than Castor, the closest red giant star to the solar system. It is located about 34 light years from Earth, so the light you see tonight left the star’s reddish surface in 1990. Nearby is Castor, which boasts a remarkable system of six stars! A small telescope will resolve Castor into two close components that take about 460 years to complete an orbit around each other. Each of these stars is itself a spectroscopic binary, while a pair of red dwarf companions loop around the other four stars every 14000 years. The entire system is about 50 light years away. At the top of the Circle is gold-tinted Capella, another multiple star system. The bright component is a spectroscopic binary with a period of 104 days. This pair is orbited by a close pair of faint red dwarf stars that need a dark sky and a large telescope to see. This system is 43 light years away. Southwest of Capella is the red-tinted star Aldebaran, which in classical star atlases marks one of the “eyes” of Taurus, the Bull. Binoculars will show Aldebaran accompanied by a V-shaped group of stars, the Hyades, but the bright star is actually about half the distance to the star cluster. Some 65 light years away, if you were born in 1959 Aldebaran is you “birthday star”. Coming back to Orion, the Circle is completed by the bright blue star Rigel, which marks one of Orion’s “knees”. Nobody on the planet today can claim Rigel as their birthday star; it is located over 860 light years away! It is bright because it is a blue supergiant star, emitting the equivalent energy of 65,000 Suns. It is yet another multiple star system, with a faint triple star system that orbits the giant primary with a period of about 24,000 years. Jupiter is gradually sliding westward as sunset creeps later each evening. You can still get a good view of the giant planet as evening twilight darkens the sky. Old Jove now sets at around 11:00 pm, so you should try to get a glimpse of him in the telescope as soon as you can spot his cheery glow. You will now find Venus low in the southeast as morning twilight brightens the sky. The dazzling planet will be only five degrees above the horizon half an hour before sunrise. On the mornings of the 21st, 22nd, and 23rd, use binoculars to look for the fainter ruddy glow of Mars less than one degree from the brighter Venus. Mars will gradually work his way into the morning sky, and will become prominent in the night sky by the end of the year.