Discover published sets by community

A stable stage of stellar evolution where nuclear fusion in the core fuses hydrogen into helium releasing energy that balances gravitational collapse. This is the longest stage in a star's cycle.

A dense, cooling stellar remnant left after a low to medium-mass star has ejected its outer layers as a planetary nebula. Fusion has ceased and it gradually cools and fades away.

A phase where helium fusion into carbon occurs in the core for medium mass stars (like the Sun), after the red giant phase, and the star is located on the horizontal branch on the Hertzsprung-Russell diagram.

The stage after main sequence where the star expands as the hydrogen fuel in the core is exhausted and shell burning occurs around an inert helium core.

A ring-shaped nebula formed from the ionized gas ejected from the upper atmosphere of a red giant star during the asymptotic giant branch phase. The exposed core heats the ejected material.

A protostar is a very young star that is still gathering mass from its parent molecular cloud. The core temperature is not yet hot enough for nuclear fusion to begin.