how do stars and planets stay up in space?

Question: how do stars and planets stay up in space?
- Keywords:
  planets,
  space,
  stars
Asked by anon-181164 to Claudia on 4 Jun 2018.
- Claudia Bonfio answered on 4 Jun 2018:
  
  This is really a nice question!
  Well, gravity holds the solar system together. Without gravity, everything would go in random directions. Then, since planets and comets are moving objects, the gravity of the Sun keeps them in their orbits.

Question: how do stars and planets stay up in space?