Deep-Sky Objects in Canis Major

NGC 2359 (Thor’s Helmet)
Image Credit: Thor's Helmet (NGC 2359) nebula by Rogelio Bernal Andreo, Ray Gralak

Canis Major may be only the 43rd biggest of the 88 recognized constellations, but it does have the distinction of containing the night sky’s most luminous star, Sirius, a double star situated 8.6 light years away with a visual magnitude of -1.24. The constellation can found to the northeast of Orion from between latitudes of +60° and -90°, and from the northern hemisphere can be seen during the winter time, although best seen at about 9 PM Local Time during the month of February, when it is highest in the sky.

In terms of deep-sky objects, Canis Major is not a particularly conspicuous constellation, but it does contain one Messier object, and a number of other objects worth observing, the most notable of which are briefly explored in this list.

NGC 2359 (Thor’s Helmet)

Located about 15,000 light years away and stretching across about 30 light years, Thor’s Helmet (image above) is a reflection nebula that surrounds an extremely hot and active Wolf-Rayet star that is expected to self-destruct in a supernova explosion in the near future, astronomically speaking. Thor’s Helmet received its memorable name as its bubble shape and extending filaments makes it resemble the helmet of the god of thunder from Norse mythology. While Thor’s Helmet can be seen as a fuzzy patch in a 6-inch or smaller telescopes, a 10-inch instrument will reveal some of the arcs stretching away from the nebula’s centre.

Messier 41 (M41, NGC 2287)

Messier 41M41 is an open cluster consisting of about 100 stars stretched across 25 light years of space, which at its distance of 2,000 light years makes it appears as big as the full Moon. It is thought to be about 190 million years old, and contains a number of white dwarfs and several red giant stars, the brightest of which lie close to its centre. Nevertheless, based on various properties of the cluster, as well as measurements of the movements of stars within it, M41 is expected to have totally dispersed in another 300 million years or so.

The cluster is located about 4 degrees almost due south of the star Sirius, and together with Nu2 Canis Majoris forms a triangle which fits inside a single binocular field of view. The most notable aspect of M41 is that in telescopic views, the stars in the cluster are arranged in curved lines, which is not apparent on photographs.

Canis Major Dwarf Galaxy

Canis Major Dwarf GalaxyThe Canis Major Dwarf Galaxy (CMa Dwarf) is an irregular galaxy that is approximately elliptical in shape, and has the distinction of being the galaxy that is closest to our solar system, being only about 25 000 light years away. Being this close, it is rather surprising that the galaxy was only discovered by an international team of professional astronomers in 2003, although it must be stated that this galaxy lies in the galactic plane, and is therefore largely obscured by dust clouds.

Nonetheless, the galaxy contains about one billion stars, among which are a large number of highly evolved red giants and several globular clusters, including NGC 1851, NGC 1904, and NGC 2808. However, since the main structure of the Canis Major Dwarf galaxy is severely degraded, most investigators believe that the globular clusters and the galaxy itself represent the remains of a larger, denser structure that was tidally disrupted by the Milky Way galaxy.

NGC 2207 and IC 2163

NGC 2207 and IC 2163This striking pair of colliding galaxies is located about 80 million light years away. In this interaction, the larger galaxy, designated NGC 2207, is pulling large amounts of gas and dust from its smaller companion, designated IC 2163, in a process that has initiated a high rate of star formation in both galaxies. They are currently in the initial stage of merging, and a billion years from now are expected to become either an elliptical or disk galaxy.

To date, four supernova events of different types have been recorded in NGC 2207, with their detection taking place in 1975, 1999, 2003, and 2013.

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