Home Articles Binocular Astronomy Binocular Object of the Month - February 2011 - M41 in Canis Major
Binocular Object of the Month - February 2011 - M41 in Canis Major

 

Canis Major is a constellation made up of many bright stars, the first five being of 1st and 2nd magnitude. It represents the larger of the two dogs that followed after Orion, the Hunter (the other being Canis Minor directly below it to the east of Betelgeuse).  When it is up, Canis Major is very easy to locate – just look for the brightest star in the sky. That is Sirius, the brightest star in both the southern and northern hemisphere. It is easily located above and east of Orion, the Hunter (or the Saucepan to us ‘Down Under’). From the map below, you can see the dog’s shape, with Sirius at the base of its neck. At 9pm this month (February) it is due north, and appears to be standing on its head.
  


α Canis Majoris (Sirius) is also called ‘The Dog Star’, though its Greek meaning is ‘scorching’ or ‘the sparkling one’. It is certainly brilliant to observe in binoculars or a small telescope. Though Sirius is intrinsically brighter than our Sun, its extreme brightness in our night sky has more to do with its proximity, being the 5th closest star only 8.6 light years away (twice the distance of the nearest star, Alpha Centauri). If it was the same distance as a Centauri, it would be four times brighter than we see it now, making it approximately magnitude –3.0. That’s almost as bright as Venus gets at its brightest.
   Sirius is actually a binary star, with a white dwarf companion. However, this is very difficult to spot with a telescope, impossible with binoculars. But it’s there.
   Our binocular object is 4o south of Sirius, or just 2° off the point one third the way up the line (west) between Sirius and the dog’s hind quarter d. M41, a very attractive open cluster 2,100 light years away, is visible to the naked eye as a patch of light with overall magnitude of 4.5. It was even known to the ancient Greeks. Aristotle in 325 B.C. counted it as one of the ‘cloudy spots’ they had identified in the sky. With binoculars (on a good night) you should be able to resolve individual stars. It contains over 100 stars in the group, the brightest of which you should see in your binoculars. With a stand or a steady hand, you should be able to discern groupings or ‘strings’ of stars, including a 7th magnitude orange giant near its centre. 
   


   M41
  

For a detailed description of more binocular objects in the southern sky, see my book "Heavens Above - A Binocular Guide to the Southern Skies". A link is provided at the bottom of this website's Home Page.