Halley's Comet

Halley's Comet

I chose Halley's Comet because it is one of the most famous comets that is most historically recorded.
Chemicals: carbon dioxide and ammonia
Location: continuously changing
Stellar Classification: 1P/Halley, short-period comet

Halley's Comet or Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–76 years. Halley is the only known short-period comet that is clearly visible to the naked eye from Earth. It lead to the first observational data on the structure of a comet nucleus and the mechanism of coma and tail formation. Halley is composed of a mixture of volatile ices – such as water, carbon dioxide, and ammonia – and dust. The missions also provided data that substantially reformed and reconfigured these ideas; for instance, now it is understood that the surface of Halley is largely composed of dusty, non-volatile materials, and that only a small portion of it is icy.

Its orbit around the Sun is highly elliptical, with an orbital eccentricity of 0.967. Halley is classified as a periodic or short-period comet; one with an orbit lasting 200 years or less. This contrasts it with long-period comets, whose orbits last for thousands of years. Periodic comets have an average inclination to the ecliptic of only ten degrees, and an orbital period of just 6.5 years, so Halley's orbit is atypical.

Sources:
 Wikipedia, the free encyclopedia. (2015, September 23). Halley's Comet. Retrieved September 28, 2015, from https://en.wikipedia.org/wiki/Halley's_Comet

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