A supermassive black hole is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (M☉). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space from which nothing can escape, including light. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center. For example, the Milky Way galaxy has a supermassive black hole at its center, corresponding to the radio source Sagittarius A*. Accretion of interstellar gas onto supermassive black holes is the process responsible for powering active galactic nuclei (AGNs) and quasars.
The first direct image of a supermassive black hole, found in the galactic core of Messier 87. This view is somewhat from above, looking down on one of its galactic jets. Rather than an accretion disc, it shows synchrotron radiation in the microwave range (1.3 mm). This light was emitted by electrons captured in the plasma vortex at the base of a jet. Radiation of this wavelength does not reveal the thermal features thought to dominate the emissions of an
An artist's conception of a supermassive black hole surrounded by an accretion disk and emitting a relativistic jet.
Artist's impression of the huge outflow ejected from the quasar SDSS J1106+1939
Artist's illustration of galaxy with jets from a supermassive black hole
A black hole is a region of spacetime where gravity is so strong that nothing, including light and other electromagnetic waves, is capable of possessing enough energy to escape it. Einstein's theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon. A black hole has a great effect on the fate and circumstances of an object crossing it, but it has no locally detectable features according to general relativity. In many ways, a black hole acts like an ideal black body, as it reflects no light. Quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly.
Direct radio image of a supermassive black hole at the core of Messier 87
An artistic depiction of a black hole and its features
Gas cloud being ripped apart by black hole at the centre of the Milky Way (observations from 2006, 2010 and 2013 are shown in blue, green and red, respectively).
A Chandra X-Ray Observatory image of Cygnus X-1, which was the first strong black hole candidate discovered