Short explanations of the astronomical terms used on this site.
Short explanations of the terms used on this site. Each term links to all the news articles tagged with it.
- Black hole
- A region of space where gravity is so strong that nothing, not even light, can escape.
- Comet
- A small icy body that forms a glowing head and tails when it comes close to the Sun.
- Cosmic microwave background
- The oldest light in the universe, released about 380,000 years after the Big Bang.
- Dark energy
- The unknown cause of the accelerating expansion of the universe.
- Dark matter
- Invisible matter that does not emit light, detected only through its gravity.
- Dwarf planet
- A body that orbits the Sun and is nearly round, but has not cleared its orbit of other objects.
- Exoplanet
- A planet that orbits a star other than the Sun.
- Galaxy
- A huge system of stars, gas, dust and dark matter held together by gravity.
- Light-year
- The distance light travels in one year, about 9.46 trillion kilometres.
- Meteor shower
- Many meteors appearing to come from one point in the sky, when Earth passes through the debris of a comet.
- Moon
- A natural satellite of a planet; with a capital M, the satellite of Earth.
- Nebula
- A cloud of gas and dust in space, often a place where stars are born or the remains of a dead star.
- Planet
- A body that orbits the Sun, is nearly round and has cleared its orbit of other objects.
- Spaceflight
- Travel into or through space, with or without a crew.
- Star
- A huge ball of hot gas that produces energy by nuclear fusion in its core.
- Supernova
- The explosion of a star at the end of its life, which can briefly outshine a whole galaxy.
- Telescope
- An instrument that collects light or other radiation to observe distant objects.
- White dwarf
- The hot, dense remnant of a star like the Sun, about the size of Earth.