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[[Image:Iu8969hu.jpg|right|thumb|300px|Artist's conception of a binary system consisting of a black hole and a main sequence star.  The black hole is drawing matter from the main sequence star via an [[accretion disk]] around it, and some of this matter forms a gas jet.]]

[[Image:Iu8969hu.jpg|right|thumb|300px|Artist's conception of a binary system consisting of a black hole and a main sequence star.  The black hole is drawing matter from the main sequence star via an [[accretion disk]] around it, and some of this matter forms a gas jet.]]

'''Black holes''' are astronomical objects that are so dense that their gravitational escape velocity would exceed the speed of light.  Because of this, no light or matter can escape them, and they appear "black"<ref>Actually, because of quantum-mechanical phenomena involving Hawking Radiation, discussed later in the article, this is not true on an extremely microscopic level, but is true for all practical purposes.</ref>.  In addition to being of great interest to scientists, they have caught the imagination of science magazines, science fiction writers, and the general public.  This is probably because of the catchy name and the extremely weird behavior of space and time in their vicinity.  This includes a number of movies:  ''Event Horizon'' (1997), ''The Black Hole'' (TV, 2006), and ''Interstellar'' (2014).  The last of those used very sophisticated mathematical models and computer rendering techniques to make show things accurately.

'''Black holes''' are astronomical objects that are so dense that their gravitational escape velocity would exceed the speed of light.  Because of this, no light or matter can escape them, and they appear "black"<ref>Actually, because of quantum-mechanical phenomena involving Hawking Radiation, discussed later in the article, this is not true on an extremely microscopic level, but is true for all practical purposes.</ref>.  In addition to being of great interest to scientists, they have caught the imagination of science magazines, science fiction writers, and the general public.  This is probably because of the catchy name and the extremely weird behavior of space and time in their vicinity.  This includes a number of movies:  ''Event Horizon'' (1997), ''The Black Hole'' (TV, 2006), and ''Interstellar'' (2014).  The last of those used very sophisticated mathematical models and computer rendering techniques to show things accurately.

Like electrons, protons, and neutrons, black holes have never been directly observed, but, as in the case of subatomic particles, evidence for their existence is overwhelming.  This evidence includes observations of radiation from accretion disks, motion of stars near the center of the galaxy, and "gravitational lensing", having all the properties that relativity predicts, around places where there are no visible objects.  Like positrons, their existence was predicted (in both cases based on relativity) before there was any actual evidence of their existence.

Like electrons, protons, and neutrons, black holes have never been directly observed, but, as in the case of subatomic particles, evidence for their existence is overwhelming.  This evidence includes observations of radiation from accretion disks, motion of stars near the center of the galaxy, and "gravitational lensing", having all the properties that relativity predicts, around places where there are no visible objects.  Like positrons, their existence was predicted (in both cases based on relativity) before there was any actual evidence of their existence.