Sirius

Sirius

I chose this star because it is the brightest star visible from Earth.
Chemicals: carbon–oxygen mixture, helium, and hydrogen
Lcoation: RA 06^h 45^m 08.91728^s | Dec −16° 42′ 58.0171″
Stellar Classification: DA2, red giant

The brightest star in the Earth's night sky, it is commonly known as the Dog Star. Located at RA 06^h 45^m 08.91728^s | Dec −16° 42′ 58.0171″ with a spectral type of DA2, it is a binary star system consisting of two white stars orbiting each other with a separation of about 20 AU . Sirius A, twice as massive as the Sun and has an absolute visual magnitude of 1.42. It is 25 times more luminous than the Sun, and Sirius B which consumed its resources and became a red giant before shedding its outer layers and collapsing into its current state as a white dwarf around 120 million years ago.

Stellar models suggest that the star formed during the collapsing of a molecular cloud, and that after 10 million years, its internal energy generation was derived entirely from nuclear reactions. The core became convective and utilized the CNO cycle for energy generation. It is predicted that Sirius A will have completely exhausted the store of hydrogen at its core within a billion (10⁹) years of its formation. At this point it will pass through a red giant stage, then settle down to become a white dwarf.

 This star is primarily composed of a carbon–oxygen mixture that was generated by helium fusion in the progenitor star. This is overlaid by an envelope of lighter elements, with the materials segregated by mass because of the high surface gravity. Hence the outer atmosphere of Sirius B is now almost pure hydrogen—the element with the lowest mass—and no other elements are seen in its spectrum.

Sources:
 Wikipedia, the free encyclopedia. (2015, September 27). Sirius. Retrieved September 28, 2015, from https://en.wikipedia.org/wiki/Sirius

Visible Spectra of the Elements. (n.d.). Retrieved September 28, 2015, from http://www.umop.net/spctelem.htm