Regions of spacetime where gravity is so strong that nothing, not even light, can escape once it crosses the event horizon.
Enormous systems containing stars, gas, dust, dark matter and other objects, held together by gravity.
Massive spheres of plasma powered by nuclear fusion. Stars produce much of the light and energy visible across space.
Extremely luminous galactic centers powered by material falling toward supermassive black holes.
Huge clouds of gas and dust where stars can form, or where material from dying stars spreads through space.
Planetary-mass objects that travel through space without being gravitationally bound to a star.
Enormous regions of the cosmic web that contain far fewer galaxies than the surrounding regions.
A mysterious form of matter that does not appear to interact with light, but its gravitational effects can be observed.
The name given to the unknown phenomenon associated with the accelerating expansion of the Universe.
Hypothetical structures that could connect distant regions of spacetime through a shortcut known as a wormhole.