Stars definitions

Astronomical unit (AU)

The average distance between the Earth and the Sun.

Light year

The distance light travels in vacuum in one year

Parsec

The distance at which a baseline of 1AU subtends an angle of 1 arcsecond

Stellar parallax

The apparent shift in position of a nearby star relative to distant background stars due to the Earths orbit around the Sun.

Parallax Angle

Half the total angular shift of the star over six months

Luminosity

The total power radiated by a star

Intensity

The power received per unit area

Inverse square law

The intensity of radiation from a point source is inversely proportional to the square of the distance from the source.

Black body

An object that absorbs all electromagnetic radiation incident on it and emits a continuous spectrum of radiation

Black-body spectrum

The characteristic continuous spectrum of electromagnetic radiation emitted by a black body

Wien’s Displacement Law

The wavelength at which a black-body spectrum has maximum intensity is inversely proportional to it’s absolute temperature

Stefan-Boltzmann Law

The total power emitted per unit area of a black body is proportional to the fourth power of its absolute temperature