On one side of the winter sky are the two bear constellations, Ursa Major and Ursa Minor, the Big and Little Dippers. On the opposite side are two lesser known star groups, the Big and Little Dogs, Canis Major and Canis Minor, rumored to be the hunting dogs of nearby Orion.
The hot bluish-white star Sirius, the Dog Star, dominates Canis Major. Sirius lies only 8.8 light-years from our solar system. This close proximity (it's the fifth closest star to our solar system) and an energy output about twenty-five times that of our sun combine to make Sirius the brightest star in the sky. Sirius has a faint, white-dwarf companion star called the Pup that can be seen using an amateur telescope under clear conditions.
During the summer months Sirius is in the sky during daylight hours and thus invisible. The ancients thought that the heat of Sirius was added to that of the sun during this period, and we continue to call the hottest portion of summer the "dog days."
Canis Minor is among the smallest constellations in the celestial sphere, basically composed of just a few stars. One of them is Procyon, its name derived from the Greek for "before the dog" because it rises before Sirius. Procyon lies only 11.4 light-years away, the fourteenth nearest star known and the fifth nearest of the stars visible to the naked eye.
To find Canis Major, draw an imaginary line through Orion's belt and extend it southeastward. The line will point just north of Sirius. Canis Minor lies between Sirius and the bright twin stars of Gemini. The stars Procyon, Sirius, and Betelgeuse, the bright red shoulder star of Orion, form a very large and almost equilateral triangle.
Planets of the Week
Saturn and Jupiter are found in the constellation Taurus, the Bull, and can be seen until an hour or two after midnight. Jupiter, large and bright, is one of the first "stars" visible when darkness falls. (The September 18 and September 25 Sky Guides provide more information on viewing our solar system's largest planets and the array of moons that surround them. Click here to read the former; click here to read the latter.)
Venus is setting more than three hours after sunset. Look in the southwestern sky after the sun goes down to spot the brilliant Evening Star, getting larger and brighter with each passing night this month. Sharp-eyed observers can even spot Venus in daylight. Mars is visible in the very early morning hours in the constellation Libra. Watch for it to brighten steadily throughout the first half of the year.
At 9:00 p.m. on February evenings, Cepheus the King, Cassiopeia the Queen, and Perseus the Hero are the most notable constellations in the northwestern portion of the sky. Cassiopeia is recognizable as a bright W shape that's visible from northern latitudes all year long. The constellation Auriga the Charioteer and its very bright alpha star, Capella, are very high in the northwest. Taurus the Bull, containing the conspicuous star cluster known as the Pleiades (or Seven Sisters) is in the west. Its other star cluster, the Hyades, which also represents a mythological group of sisters, marks the bull's face, while the bright orange star Aldebaran represents its eye.
Look toward the northeast and almost halfway up the sky to spot the Big Dipper, an asterism, or star shape, within the larger constellation Ursa Major (the Great Bear). The two stars at the end of the dipper's bowl are known as the Pointers, for a line drawn through them and extended northward points directly to Polaris, the North Star. Polaris marks the tip of the handle of the Little Dipper, which is in the constellation Ursa Minor, the Little Bear.
Gemini, the Twins, is in the southeastern part of the sky. It has two bright stars named Castor and Pollux, the twins born of an egg laid by Leda after she was seduced by Zeus in the guise of a swan. Procyon, the alpha (or brightest) star in Canis Minor, the Little Dog, is below Gemini. Most of the rest of this quadrant of the sky is occupied by faint constellations, the largest of which is Hydra, the Sea Serpent. Leo the Lion and its bright star Regulus are in the east.
Face southwest to see Orion. A very large and bright red giant star named Betelgeuse marks one shoulder, while a less bright red star called Bellatrix marks the other. The very hot bluish-white star Rigel marks one knee. The color contrast between the Orion's two brightest stars, Rigel and Betelgeuse, is evident even to the naked eye. Orion's three belt stars point toward Taurus in the west, Canis Major in the south, and Gemini and Auriga high overhead. The brightest star in the sky, Sirius, also known as the Dog Star, lies in Canis Major, the Great Dog.