Space time black holes

Black holes are very special in that the only qualities they possess are mass, charge, and angular momentum. If you know the value of those three qualities, you can calculate everything else about them, including their surface gravity. For the simplest case, a black hole with no charge and no angular momentum (i.e. non-rotating), the http://en.wikipedia.org/wiki/Surface_gravity#The_Schwarzschild_solution" provides a simple result.

Astronomers have observed black holes with masses of 18 billion times that of the Sun; you can plug that value into the Schwarzschild solution and compute the gravitational "strength" of the largest black holes known.

- Warren

 

That would be called a wormhole. They are sort of like unicorns - never actually observed.