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A massive, gravitationally bound system consisting of stars, stellar remnants, interstellar gas, dust, and dark matter. Examples include the Milky Way, Andromeda, and Triangulum galaxies.

An interstellar cloud of dust, hydrogen, helium and other ionized gases. Examples include the Orion Nebula, the Crab Nebula, and the Horsehead Nebula.

A group of stars that are gravitationally bound, often born from the same molecular cloud. Examples include the Pleiades, the Hyades, and the Globular cluster in Hercules (M13).

The structure resulting from the explosion of a star in a supernova, comprising an expanding shock wave of ejected material. Examples include the Crab Nebula (from SN 1054), the Vela Supernova Remnant, and SN 1006.

A region of spacetime where gravity is so strong that nothing, not even light, can escape from it. Examples include Sagittarius A* at the center of the Milky Way and Cygnus X-1.

An extremely luminous active galactic nucleus, powered by a supermassive black hole surrounded by an accretion disk. Examples include 3C 273 and the Twin Quasar (Q0957+561 A/B).

A type of matter theorized to account for approximately 85% of the matter in the universe and about a quarter of its total mass–energy density. It has not been directly observed, and its presence is inferred from its gravitational effects.

A highly magnetized, rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. Examples include the Crab Pulsar and PSR B1919+21.

A planet that orbits a star outside the Solar System. Examples include Proxima Centauri b, Kepler-22b, and TRAPPIST-1d.