Astro Definitions Flashcards
1 pc?
The distance at which 1AU subtends an angle of 1 arcsecond.
1 light year?
The distance EM waves travel through a vacuum in one year.
Absolute magnitude?
The apparent magnitude of an object if it were 10pc away from Earth.
Recessional velocity?
The speed at which an object is receding from Earth.
Red shift?
Increase in wavelength due to the relative recessive velocity between observer and source.
Black hole?
An object whose escape velocity is grater than the speed of light.
Dark energy?
A type of energy that fills the whole of space, and might explain the accelerating expansion of the universe.
Supernova?
An object that produces a rapid increase in brightness.
Neutron star?
Incredibly dense star made up of neutrons formed by the collapse of a red giant with a high core mass.
Type 1a supernova?
A type of supernova that always has the same peak in absolute magnitude. Often used as standard candles as apparent magnitude can be measured.
Event horizon?
The boundary of the region around an object in which its escape velocity is greater than c.
Quantum efficiency?
The proportion of incident photons falling on a light detector that are detected.
Quasar?
A quasi-stellar object that is thought to be a galactic nucleus centred around a black hole.
Doppler effect?
The change in frequency and wavelength of a wave for a source moving towards or away from an observer.
Intensity =
P / 4pi d^2
