A black hole is a region of space packed with so much matter that its own gravity prevents anything from escaping – even a ray of light. Black holes can form when massive stars run out of fuel and collapse under their own weight, creating such strong gravity that they disappear from view. Although completely invisible, a black hole exerts a gravitational pull on surrounding matter.

Find out more from HubbleSite:

• Hubble observations of black holes in NewsCenter.
• Try the “No Escape” activity in Amazing Space Online Explorations.
  http://amazing-space.stsci.edu/resources/explorations/