Astronomy 1021 Chapter 15: Chapter 15 Cosmic Perspective
2 Jan 2012
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Document Summary
All stars are made of primarily hydrogen and helium at the time they form, the differences between stars are primarily due to differences in mass and stage of life. We can measure the masses of stars in binary star systems using newton s version of kepler s third law if we can measure the orbital period and separation of the two stars. R diagram in a narrow band known as the main sequence, giants and supergiants are to the upper right of the main sequence and white dwarfs are to the lower left. Open clusters contain up to several thousand stars and are found in the disk of the galaxy, globular clusters contain hundreds of thousands of stars all closely packed together, they are found mainly in the halo of the galaxy. Apparent brightness: the amount of light reaching us per unit area from a luminous object, often measured in units of watts/m2.
