Concept
Hill Sphere
The volume in which a body's gravity dominates.
The region around a planet (or other body) where its gravity dominates that of a more massive companion — bounds where moons can orbit stably.
Overview
The region around a planet (or other body) where its gravity dominates that of a more massive companion — bounds where moons can orbit stably.
See also
Escape Velocity
The minimum speed to leave a body's gravity for good.
Black Holes
Regions where gravity stops light itself.
Roche Limit
The distance within which a body is torn apart by tides.
Lagrange Points
Five spots where gravity and orbital motion balance.
The Big Bang
How everything began, 13.8 billion years ago.
Dark Matter
The invisible mass holding galaxies together.