Milky Way

Milky Way

I chose the Milky Way because it is our own galaxy.
Chemicals: rich in heavy elements (above helium on the periodic table)
Location: 55° 31′ 47.43″ N, 5° 05′ 59.77″ W (sun)
Stellar Classification: Sb, Sbc, or SB(rs)bc (barred spiral galaxy)

The closest galaxy to the Sun is, the one we live in, is called the Milky Way or the Galaxy. It is also referred to and classified as Sb, Sbc, or SB(rs)bc (barred spiral galaxy). The name `Milky Way' comes from the band of light that is seen overhead on very dark nights. The ancients called it the Celestial River. Galileo showed that the band is actually an edge-on concentration of stars seen looking through the disk of our Galaxy from the inside. That same band looks very different when imaged at different wavelengths.

Once the distinct kinematic components of the Galaxy had been isolated, an interesting fact arose in that the chemical composition of the stars in those components also varied in a regular manner. Disk and bulge stars tend to be rich in heavy elements (above helium on the periodic table). Halo stars tend to be very poor in heavy elements.

 Changes in the chemical composition of a star are due to the initial chemical composition of the gas cloud that it was born from. This heavy elements are mostly produced by supernova explosions, gas clouds become enriched by the ejecta of supernova. The larger the number of supernova near a cloud, the richer in heavy elements it will become.


As time passes, each of the gas clouds in the Galaxy will increase in the abundance of elements such as carbon, iron, etc. So the more recent a star has been formed, the richer in heavy elements it is. This is a form of dating system for stars and it is deduced that halo stars are the oldest stars in the Galaxy since they have the lowest chemical abundances. The disk stars are the youngest since they are the most metal rich.

About  100–180 kly (31–55 kpc) in diameter with a mass of 0.8–1.5×1012 M, the milky way contains 200–400 billion stars. With the sun at it's center, the Milky Way is located at (55° 31′ 47.43″ N, 5° 05′ 59.77″ W).

Sources:
Milky Way. (n.d.). Retrieved September 20, 2015, from http://abyss.uoregon.edu/~js/ast123/lectures/lec10.html 

 Wikipedia, the free encyclopedia. (2015, September 19). Milky Way. Retrieved September 20, 2015, from https://en.wikipedia.org/wiki/Milky_Way 

 Wikipedia, the free encyclopedia. (2015, August 29). Position of the Sun. Retrieved September 20, 2015, from https://en.wikipedia.org/wiki/Position_of_the_Sun 

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