Glossary of astronomy facts for kids

This glossary of astronomy is a list of terms and concepts of astronomy and cosmology and their sub-disciplines.

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• Absolute magnetiude
• Asteroid — An asteroid is a space rock. It is a small object in the Solar System that travels around the Sun. It is like a planet but smaller. They range from very small (smaller than a car) to 600 miles (1000 km) across. A few asteroids have asteroid moon.
• Accretion disk — An accretion disk (or disc) is an astronomical term. It describes a disc of material being drawn in by gravity to a centre of mass, such as a star or black hole. As the material comes in, it spins round the central body and radiates energy.
• Active galactic nucleus — An active galactic nucleus (AGN) is a compact region at the centre of a galaxy. This central region radiates huge luminosity over the electromagnetic spectrum. The radiation from an AGN is thought to be caused by mass dragged in by the gravitational pull of a supermassive black hole at the centre of the host galaxy.