Planet  -  A large object that orbits a star and is massive enough to become nearly round.

Star  -  A massive ball of hot plasma that produces energy through nuclear fusion.

Galaxy -  A huge collection of stars, gas, dust, and dark matter held together by gravity.

Nebula  -  A large cloud of gas and dust in space, sometimes associated with star formation or stellar death.

Supernova  -  A powerful stellar explosion that can occur during the final stages of a star’s evolution.

Neutron Star  -  An extremely dense stellar remnant formed after some massive stars explode.

Accretion Disk  -  A rotating disk of hot material falling toward an object such as a black hole or young star.

Redshift  -  The stretching of light toward longer, redder wavelengths, often caused by an object moving away or by the expansion of the universe.

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Moon — A natural object that orbits a planet or another larger body.

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Asteroid — A small rocky or metallic object that orbits the Sun.

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Comet — An icy object that releases gas and dust when it approaches the Sun.

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Solar System — The Sun and all the objects that orbit it, including planets, moons, asteroids, and comets.

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Light-Year — The distance light travels in one year, about 9.46 trillion kilometers.

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Exoplanet — A planet that orbits a star outside our Solar System.

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Black Hole — An object with gravity so strong that beyond its event horizon, not even light can escape.

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Event Horizon — The boundary around a black hole beyond which nothing can escape.

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White Dwarf — The small, dense remnant left after a Sun-like star reaches the end of its life.

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Red Giant — A large, cool star formed when a star expands late in its life.

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Pulsar — A rapidly rotating neutron star that produces regular pulses of radiation.

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Quasar — An extremely bright galactic nucleus powered by matter falling toward a supermassive black hole.

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Binary Star — A system of two stars that orbit a common center of mass.

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Protostar — A young, forming star that has not yet begun stable hydrogen fusion.

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Interstellar Medium — The gas and dust found in the space between stars.

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Dark Matter — Invisible matter inferred from its gravitational effects on stars, galaxies, and

other matter.

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Cosmic Microwave Background — Ancient radiation left over from the early universe.

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Gravitational Lensing — The bending of light caused by the gravity of a massive object.

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Spectroscopy — The study of light separated into wavelengths to determine properties such as composition, temperature, and motion.

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Metallicity — In astronomy, the amount of elements heavier than hydrogen and helium in an astronomical object.

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