Astronomy Glossary

Astronomy Concepts

Parallax is the apparent shift in a star's position when viewed from opposite sides of Earth's orbit, the primary direct distance measurement method.

Units Distance

A unit of astronomical distance equal to about 3.26 light-years.

Solar System

Perigee is the point in an object's orbit around Earth that is nearest to Earth.

Solar System

Perihelion is the point in an object's orbit nearest to the Sun, where orbital velocity is fastest.

Solar System

A planet is a celestial body orbiting a star, massive enough to be rounded by its own gravity, and has cleared its orbital neighborhood of other debri...

Stellar Objects

A planetary nebula is a glowing shell of gas ejected by a dying low/medium-mass star, ionized by ultraviolet radiation from the exposed hot core (futu...

Astronomy Concepts

Polarization describes the orientation of electromagnetic wave oscillations, providing unique astrophysical diagnostics unavailable from intensity alo...

Stellar Objects

A protostar is the earliest stage of star formation, a dense core within a collapsing molecular cloud that has not yet initiated sustained nuclear fus...

Stellar Objects

A pulsar is a highly magnetized, rapidly rotating neutron star that emits beams of electromagnetic radiation from its magnetic poles.