ASTR 1514 1st Edition Lecture 24The bigger a star is the more luminous it is. We use binary star systems to measure the mass of stars, about ½ of the stars are binary systems orbiting a common center of massA less massive star moves faster on a larger orbit. Procedure for measuring the mass of a star- Measure velocities of each star from absorption line Doppler Shift- Calculate total mass of both stars using Kepler’s Third Law:- P2 = [(4)(pi)2/G(Mass1+Mass2)](a3)- Solve for the two masses- Lowest-mass stars have Mass of 0.8 Solar masses (Mass of sun)- Highest Mass stars appear to be greater than 200 Solar Masses. Spectroscopic Binaries- Observing absorption lines move in the spectrum due to the Doppler shifts- When stars are so close together that an observer will only get one spectrum from both. The Hertzsprung-Russel (HR) DiagramThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Stars fall in patters on a plot of luminosity vs temperature- Most stars fall on the Main sequence (90% of stars)- Stars have a temperature appropriate for their luminosity (much like humans have a weight appropriate to their height), however this is not always the case. - Stars near the left side of a HR diagram are hotter, and stars near the top are more luminous. - The HR diagram shows that more luminous stars are also larger stars- 10% of stars are not on the main sequence More massive stars are more luminous and
View Full Document