Of these characteristics, stellar mass is the most important characteristic. The mass of a star determines things, such as how quickly a star will consume its stellar fuel through the fusion process to the star’s final ending when it has used all of its fuel.

For low-mass stars (left hand side), after the helium has fused into carbon, the core collapses again. As the core collapses, the outer layers of the star are expelled. A planetary nebula is formed by the outer layers. The core remains as a white dwarf and eventually cools to become a black dwarf.

What changes about the star as you drag it down the H-R diagram to simulate the White Dwarf phase? the temperature decreases and the radius decreases. the gravitational potential energy of the protostar. the star swells until the surface gravity is too weak to hold material.

The stars with the longest lifetimes are red dwarfs; some may be nearly as old as the universe itself.

The star’s mass tells us how much fuel the star had when it was born, and the star’s brightness tells us how fast it is burning that fuel. We know that the star is just about to start becoming unstable–after all, the stars that are more massive have already started to become unstable.

A star can be defined by five basic characteristics: brightness, color, surface temperature, size and mass.

• Brightness. Two characteristics define brightness: luminosity and magnitude.
• Color. A star’s color depends on its surface temperature.
• Surface Temperature.
• Size.
• Mass.

There are sub-categories of Type II supernovas, classified based on their light curves. Stars much more massive than the sun (around 20 to 30 solar masses) might not explode as a supernova, astronomers think. Instead they collapse to form black holes.