Archive for May 24, 2022

Canis Major Dwarf Galaxy (CMa)   7 comments

Canis Major_Sirius

CANIS MAJOR AND SIRIUS

Constellation Canis Major is the homeland of Sirius. This star goes by the name Alpha Canis Majoris and less formally, the Dog Star. Sirius holds the title of brightest star in the sky, and it is the fifth closest known star system. Canis Major also contains the Canis Major Dwarf Galaxy, M41 – an open star cluster, and Thor’s Helmet – an emission nebula. Also included are the colliding spiral galaxies, NGC 2207, and IC 2163. They are approximately eighty million light years distant and were discovered by the English astronomer John Herschel in 1835.

Sirius –Alpha Canis Majoris

Sirius is a binary system star with an apparent magnitude of -1.42. The Sirius system is only 8.6 light years distant Sirius is a large, bluish-white star, known as a white main sequence star, and the brightest of the 2-star system. It has a mass twice that of the Sun and a luminosity twenty-five times greater. Its tiny, and thereby faint, but extremely hot, blue-white companion star, known as Sirius B, is one of the most massive white dwarfs known. With a mass of 0.98 solar masses, it is almost on a par to the Sun in this respect, and slightly smaller in size than Earth. These binary stars take approximately 50 years to orbit one another. The Sirius system is so close to Earth that if many of the well-known constellations seen in the skies of Earth were viewed from Sirius, they would appear almost identical to those in Earth’s skies.

Mythologically speaking, Canis Major is allied with the world’s fastest canine, known as Laelaps This dog could never fail to capture any prey it was in pursuit of. The god Zeus bestowed this dog upon Europa as a gift, together with a spear that was incapable of missing its target. Laelaps was given a position in the nocturnal sky and became the Canis Major constellation.

Sopdet – Egyptian goddess of the Sky and Stars, personifies Sirius the Dog Star. Her symbols are stars and dogs. The arrival of Sirius in the sky heralds the approach of New Year and this event is celebrated with a festival – ‘The Coming of Sopdet.’ In Greece she is known as the Greek goddess Sothis, and Sirius, as Seirios. – the celestial dog in the constellation of Canis Major – the Great Dog and the Guard dog of Orion.

Canis Major Dwarf Galaxy (CMa Dwarf)

Picture2

The Canis Major Dwarf Galaxy (CMa Dwarf), also known as “Overdensity,” is a small, irregular galaxy, roughly elliptical in shape, and thought to be the closest galaxy to our location in the Milky Way. It is roughly 25,000 light years distant from our solar system and 42,000 light years from the Galactic Centre of the Milky Way. The next closest galaxy (70,000 light years) is the Sagittarius Dwarf Elliptical Galaxy (SagDEG) discovered in 1994.

The Canis Major Dwarf Galaxy was first discovered in 2003 by an international team of astronomers using data derived via the “Two-Micron All Sky Survey (2MASS)” (infrared survey). Observation of CMa is difficult due to its masking by the stars, dense dust, and vapour in the of our galaxy.

Its “irregular galaxy” status is due to it being gradually torn asunder by the gravitational force of our own galaxy. Gravitational interactions between the two galaxies, have resulted in extensive, astral streams – formed by tidal forces, which were plundered from the Canis Major dwarf galaxy. They went on to wind themselves three times around the Milky Way, forming a 200,000-light year-long strand-like edifice consisting of a nebulous circle of stars, vapours, and dust which encircles the Milky Way, and is known as the “Monoceros Ring”.

Monoceros - the Unicorn

It was during the investigation of this ring – discovered in 2002, by astronomers conducting the “Sloan Digital Sky Survey,” that the Canis Major Dwarf galaxy was discovered, one year later in 2003. As a result, it swiped the title of “closest galaxy to our location in the Milky Way” from the Sagittarius Dwarf Elliptical Galaxy (SagDEG)

References:

https://imagine.gsfc.nasa.gov/features/cosmic/nearest_galaxy_info.html

https://www.wise-geek.com/what-is-the-canis-majoris-dwarf-galaxy.htm

https://www.constellation-guide.com/constellation-list/canis-major-constellation/

https://astronomy.swin.edu.au/cosmos/c/Canis+Major+Dwarf