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(The Great Dog)
       
 
 

The cosmic hound of the sky ready to pounce on any prey, specifically Lepus the hare. From a mythological viewpoint, this dog is the pet of Orion the Hunter. This certainly sounds plausible as Orion's Belt points to the heart of Canis Major, the brightest star in the sky, Sirius the Dog Star.

This star is easily visible from northern skies and the upper half of this constellation is visible from southern states in America. The brightness of Sirius is so great that it has a magnitude of -1. The only other celestial object that is brighter is planet Venus. Another miraculous fact related to Sirius is that it is very close at about 9 light years away. Compare this to the Hercules Galaxy Cluster which is a mindbending 500 million light years away. The distance between these two objects is almost infinitesimal! Sirius also has a near invisible companion nicknamed the Pup. Formally this star is known as Sirius B and was discovered in 1862 by Alvan Clark.

         
 
                   
  Thor's Helmet Nebula    
       
    The coruscating fusion of colours that is the Thor's Helmet is an unforgettable sight that will stay with you for all of eternity. The vivid colours are only revealed in long exposure pictures such as the one above. The turquoise parts contain oxygen and pink signifies the presence of hydrogen.    
Image copyright R. Gendler
     
    M41:
    Right next to Sirius, this magnitude 4.5 open cluster consists of 100 stars which also include a dozen red giants. This cluster is very conspicuous and might have been seen by Aristotle in 325 BC.
         
NGC 2362:
Tau Canis Majoris is a gleaming beacon of light that is encircled by the cluster
NGC 2362. This cluster is very young at 25 million years old and the cluster includes a number of five dozen stellar bodies.
   
Thor's Helmet (NGC 2359):

A name like this implies a sense of strength and nobility and this 'mighty' nebula definitely incorporates these values. On the outside this nebula looks peaceful and ethereal. On the inside it is a miasma of activity with violence and stellar carnage produced by a special type of star, a Wolf Rayet type. This violent behaviour includes extremely fast stellar winds that blow out a bubble that the interior parts of the nebula is comprised of.

Wolf Rayet stars are extremely rare and are incredibly luminous and hot as well as being massive in size. In some Wolf Rayet bubbles, the bubble interacts with the interstellar medium picking up additional gas that isn't as bright as the main bubble. This could possibly be the case with NGC 2359. Other Wolf Rayet bubbles include the Crescent Nebula in Cygnus and RCW 58 in Carina.

Thor was a Norse god and was responsible for creating mountains and thunder and lightning. On his flying chariot driven journeys he encountered many obstacles and the same can be said of the original bubble that was produced by the winds. The original bubble crashed into a molecular cloud and more complex features and filamentary strands were created that are currently visible attached to the main structure.

Some people have likened the appearance of the nebula to one of a duck, which is a far cry from the warlike Thor's Helmet.

   
NGC 2207 and IC 2163:
An astounding interacting galaxy pair that never fails to delight observers. NGC 2207 is the larger of the two and is fairly normal in appearance. The same cannot be said of the smaller IC 2163, its southern spiral arm is heavily distorted due to gravitational interactions with its larger neighbour. In fact it is actually behind
NGC 2207, the parts that are close to NGC 2207 are heavily reddened due to the light coming from it being reddened by dust in the spiral arms of NGC 2207.
   
Ced 90:
Forming the southern part of the Seagull Nebula in Monoceros, this pink and purple rectangular blob is brighter on the right side. A bright star protrudes the central part of the brightest part and this provides nice contrast. It also has a mild reflection component that can be seen more clearly in photographs, this was noticed by Sidney van den Bergh who included this nebula in his catalogue of reflection nebulae and catalogued it as vdB94.
                 
NGC 2217:

An incredible sight through large telescopes, NGC 2217 is a highly attractive barred spiral galaxy that glows at a fairly bright magnitude of 12.

A ring of stars surrounds the main structure, this is the least conspicuous part of this galaxy.

                 
Sh2-308:

One of the rarest of celestial treasures, this oval shaped nebula is a Wolf Rayet bubble blown out by the star EZ Canis Majoris, which is situated north of the much brighter 4th magnitude Omicron 1 Canis Majoris. It is relatively obscure in comparison to its more well known cousin, the Thor's Helmet although it has garnered interest in professional circles as it is one of the two Wolf Rayet bubbles where x-ray emission is present. Unexpectedly, there is a tiny gap between the rim of the optical shell and the edge of the x-ray emission. The other Wolf Rayet bubble with x-ray emission is the Crescent Nebula, although this differs as the x-ray emission extends towards the optical rim and not beyond it.

Another difference between Sh2-308 and the Crescent Nebula is the age, it is 70 000 years old as opposed to the 24 millenia that the Crescent Nebula has occupied in the 13.7 billion years of the Universe. Rather perplexingly, despite being older, Sh2-308 is actually in an earlier evolutionary stage than the Crescent Nebula.

Observations and research suggest that Sh2-308 is composed of three distinct parts, similar to the multiple layers that form an onion. The interior is comprised of red supergiant wind that has been swept up. This is enveloped in undisturbed supergiant wind, which is encircled by a shell of shocked wind. In the case of the more evolved Crescent Nebula, all the supergiant wind has been swept up into a singular shell that has become fragmented allowing some of the stellar wind to break through. This is beautifully demonstrated in very long exposures of the nebula with specialised filters that highlight doubly ionized oxygen and hydrogen alpha emission.

Despite the attention it has received in the professional realm, many amateur astronomers are unfamiliar with this intriguing and curious object. As with most obscurities, the unfamiliarity stems from the faint nature. Fortunately it is easily located as it is adjacent to Omicron 1 Canis Majoris, which is visible with the naked eye. An invaluable aid in glimpsing the dim shell is an OIII filter as this greatly improves contrast.

                 
Wolf Rayet bubble Sh2-308      
Sh2-308 is a large Wolf Rayet bubble that was one of the first to be identified and was blown out by the Wolf Rayet star, WR6. Its appearance differs from the Thor's Helmet as it is a circumstellar bubble.
The area near the top is a 'breakout', this is a region where the stellar wind is breaking through the gaseous shell. The bright yellow star is Omicron 1 Canis Majoris.
     
Image copyright D. Goldman
 
Canes Venatici   Canis Minor