The constellation of the Big Dog is where you'll find the brightest star in the sky, Sirius. The Dog Star is just one of the many luminous stars in Canis Major.
For those in the Northern Hemisphere, winter is the best time to observe the constellation of Canis Major, the Big Dog. It rises just above the southern horizon, heading from southeast to southwest. Because it is so low in the sky, its many bright stars do not get much notoriety except for one, Sirius, because it is the brightest star in all the heavens as seen from Earth.
Finding Sirius and Canis Major
Canis Major is easily found because of bright Sirius and its location near Orion, which is one of the easiest constellations to spot in the night sky. Canis Major sits to the lower left of the form of Orion. Once you've seen the bright star Sirius just beyond Orion's right foot, you can trace out the shape of the dog. Sirius marks the spot where his collar would be. His head is a dimmer triangle but bright stars mark his front foot and his rear flank and tail.
The Stars of Canis Major
Sirius, sometimes known as the Dog Star because of its home constellation, is a magnitude -1.44. It owes its brightness to its location. It lies a mere eight and a half light-years away. Alpha Canis Majoris (Sirius) is a binary star system. Sirius A is the younger, hotter, and brighter star, with Sirius B playing the part of the dim companion.
Three unmemorable stars lie near Sirius, marking the dog's head. They range from magnitude 4.0 to 4.3. Cities that suffer from light pollution make the dog's head difficult to see.
The fourth brightest star in Canis Major is five and a half degrees away, marking the front foot of the dog. This star is Mirzam, a magnitude 1.98 star that is much farther from us than Sirius. Mirzam lies about 500 light-years away.
The second brightest star in Canis Major is toward the back portion of the dog, where its hind leg would connect with its body. This star is Adhara, a magnitude 1.5 beacon lying 430 light-years away. Just above on the Big Dog's body, where the tail connects to the torso is the star Wezen, a magnitude 1.83 light that would be much brighter than Sirius if it were closer. Wezen lies more than 1700 light-years away.
The last notable bright star in Canis Major is that which marks the tip of the Big Dog's tail. Aludra is a magnitude 2.45 star lying farther than all the other bright stars in Canis Major, at 3200 light-years.
Deep-Sky Objects in the Big Dog
There is only one Messier object in Canis Major, and that is M41. M41 is a relatively bright open cluster that shines at magnitude 4.5. M41 lies about four degrees from Sirius, in the general location of what would be the dog's heart.
One last notable object in Canis Major lies in the corner of the constellation above the dog's head, almost nine degrees northeast of Sirius. This is NGC 2359, or Thor's Helmet. This strange-looking nebula has a Wolf-Rayet star at its core. The nebula has a central bubble shape, with appendage-like tentacles streaming out on various sides. Lying about 15,000 light-years away, this nebula is around 10th magnitude and can be picked up in smaller telescopes.
