Astronomy Dictionary

Browse through Sky at Night Magazine’s comprehensive astronomical dictionary, with over 300 entries.


When a planet is 90 degrees from the Sun in the sky.

Quantum theory

This is the study and respective theories on how the Universe is put together on a tiny sub-atomic scale. It’s the dream of many scientists to combine quantum theory with the theories that explain the large scale Universe in one unified theory.

Quark star

A theoretical type of massive neutron star that is so dense that matter is broken down to its constituent particles. Quarks are the hypothetical constituent particles of subatomic particles, like neutrons.


A very distant active galaxy that emits large amounts of energy from its centre as electromagnetic radiation. The word is a contraction of ‘quasi-stellar radio source’.

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