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Ken Tapping, April 8, 2009
In the sky this week...
> Venus, Mars and Jupiter are low in the sunrise twilight. Venus should be the easiest to find.
> The Moon will be Full on April 9, "The Moon of Meltwater".
After the spectacular constellations and bright stars of winter, the sky we see on a clear, dark night in spring is far more low-key. However, after months of winter, it is a pleasure to go outside without gradually losing the feeling in your fingers or toes.
Start at the Big Dipper, the brightest part of the constellation of Ursa Major, the "Great Bear", which is almost overhead at this time of the year. If you follow the line of the two stars opposite the handle upwards, out of the Dipper, you'll end up at the Pole Star, or North Star. Logically, that pair of stars: Dubhe and Merak, are known as "The Pointers". However, this time we will follow the line of the Pointers in the opposite direction, downward, roughly southward. After a distance of roughly five times the distance between Dubhe and Merak you'll find a grouping of stars that looks like a crouching lion. This is the constellation of Leo, "The Lion", which is one of the rare constellations that actually resembles what it's named after. At the moment Leo is being distorted by the presence of the planet Saturn, which is easy to identify because it is gold-coloured and not twinkling. Saturn is worth a look. Right now we are almost in line with the rings. Through a small telescope it looks like an orange with a pencil stuck through it.
The brightest star in Leo is Regulus, in the lion's breast. The second brightest is Denebola, at the root of the lion's tail. In Greek legend, Leo was the Nemaean Lion, which was conquered by Hercules. Leo was special to the Egyptians because when the Sun was in line with this constellation, the Nile started its annual flooding.
If you scan to the right from Regulus, after a bit less than the distance between Regulus and Denebola, you arrive in an area of faint stars with a hazy blob in it. You're in the constellation of Cancer, "The Crab", and your binoculars will show that blob to be a cluster of thousands of stars. It is known as Praesepe, "The Beehive".
Now head from Regulus to Denebola and continue on, curving downwards. That moderately bright, white star is Spica, the brightest star in Virgo. The Greeks and Romans identified Virgo with Persephone or Ceres, the goddess of the harvest. In the old star maps, where the constellations are shown with their mythic figures added, Virgo is usually shown as a lady holding a handful of wheat.
Virgo, and the faint constellation directly above it, Coma Berences, or "Berenice's Hair", is interesting because when we look in that direction we are looking almost perpendicular to the plane of our galaxy, right out into intergalactic space. A largish backyard telescope will show the area filled with countless faint blobs, all galaxies, each containing billions of stars.
Go back to the Dipper and follow the curve of the handle into the eastern sky. You'll arrive at the bright, golden star Arcturus. This is the brightest star in Bootes, "The Herdsman". In 1933 light from this star was used to open the Chicago "Century of Progress" exposition, an event that was really opened by a star!
Ken Tapping is an astronomer at the National Research Council Herzberg Institute of Astrophysics (NRC-HIA), and is based at the Dominion Radio Astrophysical Observatory, Penticton, BC, V2A 6J9 Tel (250) 493-2277, Fax (250) 493-7767,