ASTR 1P02 Lecture Notes - Molecular Cloud, White Dwarf, Cygnus X-1
17 Sep 2013
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Document Summary
To find out about the process of star formation one should look at the young. Lifetime of a star= amount of fuel/energy output. The youngest stars are located at the top left corner of the main sequence they appear as bluish (high surface temp) and they have very high luminosities. The observations show that such stars are surrounded by gas and dust of interstellar material (ism) Gas: 74% by mass is hydrogen (h, 24% by mass is helium (he, 2% by mass all other elements. When the clouds of interstellar material are observed in the visible part of the spectrum (wave lengths: 400mm 700mm). The starlight is absorbed by dust particles in the nebula. They are bluish for the same reason that the sky appears to be blue on a clear sunny day- molecules (and dust) in the air scatter blue light more efficiently than the longer wavelengths.
