From Citizendium, the Citizens' Compendium
- Astronomy : The study of objects and processes in the observable universe, e.g. stars, planets, comets or asteroids.
- Astrophysics : Hybrid of Physics and Astronomy that attempts to explain the physical workings of the celestial objects and phenomena.
- Antares : The brightest star in the constellation of Scorpius and the sixteenth brightest star in the nighttime sky.
- Black hole : Area of space-time with a gravitational field so intense that its escape velocity is equal to or exceeds the speed of light.
- K-type star : Star which is usually slightly cooler than our Sun and often orange in colour; includes hydrogen-burning 'main sequence' stars and older, giant stars such as Arcturus.
- Magnitude (astronomy) : Logarithmic measure of the brightness of an object, measured in a specific wavelength or passband, usually in optical or near-infrared wavelengths.
- Nova (astronomy) : Variable star in the class of cataclysmic variable stars, which is normally very faint but occasionally erupts in an immense explosion, increasing its brightness a thousand to tens of millions of times; similar but unrelated to supernovae.
- Parallax : the apparent change in the position of an object resulting from a change in position of the observer.
- Red dwarf (star) : Small and relatively cool star, of low luminosity, being in the main sequence either late K or M spectral type.
- Stellar classification (astrophysics) : The categorization of stars by various properties.
- Sun : The star that defines our solar system.
- Variable star : A star whose apparent brightness exhibits periodic variations
- Galaxy : Gravitationally bound system of stars typically contain ten million to one trillion stars.
- Globular cluster : Spherical, globular collection of stars that orbits a galactic core as a satellite, and is generally smaller in size than a galaxy.
- Universe : The summation of all particles and energy that exist and the space-time in which all events occur.