4 October 2014

Constellation Canis Minor

Orion's two hunting dogs, Canis Major (meaning Great Dog) and Canis Minor (meaning Small Dog), run close behind (East of) Orion, one flanking each side of the faint constellation of Monoceros (meaning 'single horn'...the Unicorn)
The link between the three constellations of Orion, Canis Major and Canis Minor) has a special name - The Winter Triangle, because it is prominent in the Northern Hemisphere sky in winter:

(Image adapted from Stellarium program)

(See Software Bisque 'Tom's Corner' for more
asterisms [shapes made by the stars] in Orion

I like this image from Nature that shows the three constellations off in all their glory (the constellation of monoceros, however, isn't at all obvious in the middle of the triangle):

Joining together even more constellations is the Winter Hexagon, which links six constellations: Orion, Canis Major, Canis Minor, Gemini, Auriga and Taurus...humans! Forever making shapes out of everything:

Of the two dogs, I'll start with Canis Minor, because it isn't a very large constellation, and hasn't as many objects associated with it...

Canis Minor

Canis Minor is the highest in the sky in late February. From the above image, you can see, since we know where Orion and Gemini are (from previous Constellations), we can use these to find Canis Minor, the smallest of the two dogs.
If you follow Orion's two shoulder stars, Bellatrix (top right) and Betelgeuse (top left) across to the left, to beneath the middle of Gemini (about under the star called Mekbuda) there are two stars that stand out, and this is the constellation of Canis Minor:

Yep! That's all there is to it really. This small asterism really consists of not much more than two bright stars and not a lot of deep sky objects (those it does have are so faint (magnitude 15) they can't be seen with the naked eye).
The two main stars are Procyon and Gomeisa:

Canis Minor without the background picture:

(If you still want more help finding it, go to Wikipedia, you can see a cool image where the lines marking the constellations fade in, making it clearer whare Canis Minor is)

Main Stars of Canis Minor


At first Gomeisa (meaning 'bleary-eyed' (referring to a woman) and also called Beta Canis Minoris) doesn't appear to be one of the most exciting stars in the sky. However, it's a fast-spinning, blue-white, main sequence (hydrogen burning) star about 3.5 times the mass of our Sun. If you want to remember one thing about this star to tell your friends, it might be that it spins so fast some of its atmosphere has come off its equator and created a halo around the star (It's what they call a Be star). It is about 170 light years away.

(Image of Gomeisa: The Electronic Sky)


Procyon, sometimes called the Little Dog Star, has the honour of being the eighth brightest star in our sky. It's name means 'before the dog', because it rises an hour before the Dog Star, or Sirius, in Canis Major (I'll get to that in a minute) in the evening:

 (Image from La Bitacora de Galile ...if you want to
see all ten brightest stars, go to this page!)

As we have already found in other constellations, what looks like one star is actually a binary made up of Procyon A (a normal star like our sun, but possibly finished with burning hydrogen in its core and has started to expand as it burns fuel outside the core ) and Procyon B (a dwarf star). There's an excellent animated demo. of the two stars orbiting each other at Solstation.com.

(Other images from Solstation.com)

Although Procyon is only about twice the mass of the sun, it is about 7.5 times the brightness (luminosity) of the sun, and is particularly bright because it is very close to us in astronomical terms...only about 11.5 light years away!

I love this 3-D image modelling the closest stars, showing Procyon at the top:

Here is a close-up of the Canis Minor constellation with my added notes (original from Walk Mag):

Deep sky objects of Canis Minor

Even though the Milky Way runs through Canis Minor, strangely there are not many deepsky objects, only four recorded, and none are readily visible with the naked eye:

If you have a good telescope, it might be possible to see some of these fainter objects (images courtesy of The Night Sky website) :

In particular, around Canis Minor:

Two of the recorded objects, whilst once believed to be star clusters, are actually faint groups of unrelated stars: NGC 2459 (a group of about 5 stars, though some think it's an open cluster, ie they are related) and NGC 2394 (a group of about 15 stars, also possibly an open cluster) (Neither has a proper name, that I can find). Here's NGC 2459:

And here's NGC2394, its stars in an S shape, next to the Eta star:

The other 'two' objects are galaxies. There's what's called a lenticular galaxy (disc-or lens-shaped galaxies, shaped a bit like spiral galaxies, which have little interstellar matter and don't have much star formation), called NGC 2508, which is on the border of constellation Cancer, the crab (see the first image of this 'Deep sky objects' section,in which the galaxy is marked just above and to the left of the 'C' of the label 'Canis Minor')

and a pair of galaxies which are gravitationally interacting with each other, originally only recorded as a single object, NGC 2402, about 245 million light years away from us, and may be separated by only  a few hundred thousand light years from each other.

Canis Minorids

Though this meteor shower doesn't have as many meteors as once it did, there is still some meteors radiating from somewhere near the star 11 Canis Minor, a white dwarf. The not very spectacular shower lasts from about the 4th to the 15th December each year, and has its peak about the 8th.  As with the Geminids, the shower is the result of the Earth passing through the debris from a comet, either comet Nicollet-Pons or else comet Mellish.

[Edit: I forgot to add the distances of the two stars - outrageous! Here they are now :-) ]

Distance of main stars in Canis Minor

Previous Constellation: Gemini

Next Constellation: Canis Major

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