(spectroscopic parallax) < < prev   next > > (Chapter 16)
To measure the mass of a star, we use Kepler's law and the momentum equation (or center of mass equation) for binary stars. When we graph the luminosity vs. mass of main sequence stars, we get something like the graph shown below.
This graph is called a log-log graph because the axis divisions are powers of 10. The slope of the line shown in this graph is 4. This means that the luminosity is proportional to mass to the 4th power. This is called the mass-luminosity relation and is expressed mathematically as
If you double the mass of a star, by what factor does its luminosity increase?
Therefore, the mass-luminosity relation gives us the following method for calculating the mass of a main sequence star. (1) Determine the luminosity of a star and (2) calculate the mass of the star.
Note: to keep spammers out, the feedback form requires you to type the class name, such as PHY1050, in order to submit feedback.
Class (enter PHY1050):
On a scale of 1 to 5 stars, with 5 stars being the best, how do you rate this lesson?