Topic Menu

Cyber-chess a chess instruction site

The mass of a star

Making a measurement of the mass of binary sytem stars is relatively easy.

Binary systems have two or more stars that are pulling each other into orbits of each other. By measuring the size of the orbits, the stars' orbital speeds, and their orbital periods, astrophysicists can determine exactly what the masses of the stars are.

They can take that knowledge and apply it to similar stars that are not in multiple systems.

It is also easy to measure the luminocity and temperature of any star. A plot of luminocity versus temperature for a set of stars is called a Hertsprung-Russel (H-R) diagram, and most stars lie along a thin band in this diagram known as the 'Main Sequence'. These are stars that are fusing hydrogen within the core.

Stars are found to be arranged according to mass on the Main Sequence. Massive stars are hotter and brighter than their smaller counterparts. If a star falls within the Main Sequence, we therefore immediately know its mass.