IB Physics E.5.2 Evolution of Stars Key Definitions

A black body is an idealized object that absorbs all radiation falling on it and emits radiation based on its temperature.

A region of spacetime where gravity is so strong that nothing, not even light, can escape from within its event horizon. Formed when the remnant core of a massive star exceeds about 3 solar masses (the Oppenheimer-Volkoff limit).

The maximum mass of a white dwarf, approximately 1.4 solar masses. Above this limit, electron degeneracy pressure cannot support the star and it collapses further into a neutron star or black hole.

A scatter plot of stars showing luminosity on the vertical axis against surface temperature (decreasing to the right) on the horizontal axis, used to classify stars and trace their evolutionary paths.

The state of a star in which the outward radiation pressure from nuclear fusion exactly balances the inward gravitational force, keeping the star stable in size.

The diagonal band on the HR diagram occupied by stars that are actively fusing hydrogen into helium in their cores, including the Sun. Stars spend roughly 90% of their lives on the main sequence.

The collapsed core of a massive star left after a supernova, composed almost entirely of neutrons and supported by neutron degeneracy pressure. Typically around 10 km in radius despite having a mass of one to three solar masses.

Nuclear fusion is the process where two light atomic nuclei combine to form a heavier nucleus, releasing an extraordinary amount of energy.

A catastrophic explosion of a massive star triggered when the iron core can no longer support itself against gravity and collapses, releasing enormous energy and dispersing the star's outer layers into space.

The dense, Earth-sized remnant of a low- to medium-mass star after it has shed its outer layers. Supported against further collapse by electron degeneracy pressure, with a maximum mass of about 1.4 solar masses (the Chandrasekhar limit).