Concept
The Habitable Zone
Where liquid water can exist on a planet's surface.
The orbital region around a star where temperatures allow liquid water — often nicknamed the 'Goldilocks zone'.
See also
Hydrosphere
All the liquid water on a planet.
Black Holes
Regions where gravity stops light itself.
Termination Shock
Where the solar wind slows from supersonic to subsonic.
Obliquity
The tilt of a planet's axis to its orbit.
Lagrange Points
Five spots where gravity and orbital motion balance.
Photon Sphere
Where light itself can orbit a black hole.