Do scientists and astronomers know exactly where each black hole is or is it possible for satellites or astronauts to be pulled into a black hole that was not known?
We would be able to tell if a black hole came close enough to the Earth that satellites or astronauts could fall into it as a black hole that close would severely disrupt the orbits of the planets! It is not thought that this is likely to happen. Black holes seem quite rare, so the chance of there being one anywhere near us is very small. Space is very big.
Karen was a graduate student at Cornell from 2000-2005. She went on to work as a researcher in galaxy redshift surveys at Harvard University, and is now on the Faculty at the University of Portsmouth back in her home country of the UK. Her research lately has focused on using the morphology of galaxies to give clues to their formation and evolution. She is the Project Scientist for the Galaxy Zoo project.