Classification of stars Key Terms

Spectral line

A narrow wavelength band where a star’s spectrum shows absorption or emission, indicating the presence of a specific element.

Spectral class

A classification of stars based on the pattern of absorption lines, which correlates with surface temperature and chemical composition.

luminosity

luminosity: a specific A-Level Physics term for Hertzsprung-Russell diagram. Use it to support interpret luminosity and temperature axes on the HR diagram. by linking the named observation, graph, spectrum or measurement to the correct astrophysics conclusion. This definition is intentionally tied to Hertzsprung-Russell diagram, so it is not a generic astronomy label.

Hertzsprung-Russell diagram

A graphical representation of stars plotted according to their luminosity and temperature, used to classify stars and understand their evolution.

luminosity

luminosity: a specific A-Level Physics term for Hertzsprung-Russell diagram. Use it to support classify stars by position on the HR diagram. by linking the named observation, graph, spectrum or measurement to the correct astrophysics conclusion. This definition is intentionally tied to Hertzsprung-Russell diagram, so it is not a generic astronomy label.

apparent brightness

The amount of light received from a star per unit area, which decreases with distance from the star.

main sequence

The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness, where stars spend the majority of their lifetimes fusing hydrogen into helium in their cores.

post-main-sequence evolution

Post-main-sequence evolution refers to the changes that occur in a star after it has exhausted the hydrogen in its core, leading to different paths such as red giant, supernova, or the formation of white dwarfs, neutron stars, or black holes.

luminosity

luminosity: a specific A-Level Physics term for Hertzsprung-Russell diagram. Use it to support link stellar mass to life cycle outcomes. by linking the named observation, graph, spectrum or measurement to the correct astrophysics conclusion. This definition is intentionally tied to Hertzsprung-Russell diagram, so it is not a generic astronomy label.

apparent brightness

The observed brightness of a star as seen from Earth, dependent on distance and luminosity.

supernova

A supernova is a powerful and luminous explosion that occurs at the end of a massive star's life cycle, resulting in the ejection of its outer layers.

massive star

A massive star is a star with a mass significantly greater than that of the Sun, typically greater than eight solar masses, which leads to different evolutionary paths including supernova formation.

Neutron Star

A neutron star is a compact remnant of a massive star that has undergone a supernova explosion, consisting primarily of neutrons and exhibiting extremely high density.

Compact Remnant

A compact remnant is the dense core left behind after a star has exhausted its nuclear fuel and undergone a supernova, which can be a neutron star, black hole, or white dwarf.

black hole

A region in space where the gravitational pull is so strong that nothing, not even light, can escape from it.

event horizon

The boundary surrounding a black hole beyond which no information or matter can escape.

supernova

A supernova is a powerful explosion that occurs at the end of a star's life cycle, resulting in a dramatic increase in brightness and the ejection of its outer layers.

neutron star

A neutron star is a compact stellar remnant composed primarily of neutrons, formed from the collapsed core of a massive star after a supernova explosion.