Astronomy 1021 Lecture Notes - Lecture 9: Inverse-Square Law, Chromosphere, Balmer Series
29 Feb 2016
School
Department
Course
Professor
Document Summary
The sun is a big ball of hot gas held together by its own gravity. Deep inside core: energy produced by nuclear fusion. Energy slowly travels outwards until eventually it escapes from the surface" through radiation. The distance to the sun was first measured using transits of venus. What information do we need to measure the suns luminosity: brightness at earth + inverse square law, luminosity: amount of power an object radiates, apparent brightness: amount of light that reaches measuring position. We can determin the suns composition from the solar spectrum: strength of absorption lines: related to amount of element. The sun is primarily made of hydrogen and helium: hydrogen and helium make up more than 98% of the suns mass, helium got its name because it was discovered first in the suns spectrum. Corona: millions of k, very low density, source of x-rays.
