April 2012 Constellation of the Month: Canis Major

In early April 2012, soon after sunset, you can see 4 very bright points of light. Venus is by far the brightest of these. It is in the mid-west part of the sky -- in our Feb. 2012 Constellation of the Month, Taurus. Jupiter is low in the West. And Mars is towards the Southeast in the constellation of Leo, which we'll cover next month.

The southernmost bright object is the only star of the 4. This is Sirius, the Dog Star, in the constellation of Canis Major (Big Dog) -- which is southeast of our March 2012 Constellation of the Month, Orion. Sirius is the brightest star in the sky -- at any time of year, northern or southern hemisphere. It is brighter than Mars right now. Although Sirius appears notably brighter than Betelgeuse in Orion, it is only 23 times as bright as the Sun. As we said last month, Betelgeuse is 40,000 time brighter. So Sirius is much closer -- only 8.6 light years (about 50 trillion miles) away.

M41 is an open cluster of 8,000 stars south of Sirius. It is easily visible with binoculars.

The band of the Milky Way passes through Canis Major, although it is less prominent there than in our Dec. 2011 Constellation of the Month, Cassiopeia, and the summer constellations. This is because when we look at Canis Major, we are looking away from the center of the Milky Way galaxy, and there are fewer stars along the plane of the galaxy in that direction.