Shining brilliantly in the winter sky is the gem of the night, Sirius. It has been called the Dog Star, as it is the brightest star of the Big Dog constellation, otherwise known as Canis Major. At about 8 p.m. in late January, look for Sirius not quite halfway up in the southeast. It gleams like a blue-white diamond. It is due south at around 10:30 p.m. at this time of year. The constellation Orion, with its famous trio of “belt stars,” is to the upper right.
The ancient Egyptians revered Sirius as its rising just before dawn marked the time of year when the Nile River would flood. The ancient Greeks referred to the “Dog Days” of summer when Canis Major was in the daytime sky, hiding beyond the blue. The Polynesians considered Sirius an important navigation star around the Pacific Ocean.
It is one of the nearer stars, only 8.6 light years distant. Orbiting Sirius is a much fainter and smaller star known as Sirius B, nicknamed the “Pup.” A fairly large telescope is needed to detect the Pup. The biggest difficulty in seeing it is the nearness of its overwhelmingly bright companion star. The Pup star was first detected in 1862 through a newly crafted refractor telescope with a precision 18-inch lens. It had been suspected since deviations in the path of Sirius were observed starting in 1834, raising suspicion that the gravitational effect from an unseen orbiting star was pulling on Sirius. The Pup is an extremely dense white dwarf star, some three times the size of Earth yet having 250,000 times the Earth’s mass. One cubic inch of the star’s material would weigh a ton.
Sirius blazes at magnitude -1.43. Sixth magnitude is commonly the faintest star you can see without optical aid, though the sky must be dark. The sun, by contrast, is magnitude -27, and the full moon is -12.
If you have binoculars, or a telescope, see how dazzling Sirius appears. Scan a short distance below (south) of Sirius until you locate a very nice, rich open star cluster known as M41. Binoculars will show it as a fuzzy spot; a small telescope will break it into a host of stars, with a pretty red one in its midst.
All this and much more is waiting in the night sky for you, if you have but eyes to see and a heart to appreciate it. This show is waiting the next clear night and is free - no cable TV bill and no commercials. No Internet hook-up is needed. The “sky show” above is also very family-oriented!
New moon is on Jan. 30. Enjoy dark, moonless evenings all week. Jupiter shines bright in the eastern sky in the evening and is due south, high up (for mid-Northern latitudes) around 11 p.m.
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Keep looking up!