Quantum Technology Research

A black hole is a region of spacetime where gravity is so
strong that nothing, including light or other electromagnetic
waves , has enough energy to escape it. The 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 . Although
it has a great effect on the fate and circumstances of an
object crossing it, 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.
Moreover, 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.The presence of a black hole can be inferred through its
interaction with other matter and with electromagnetic
radiation such as visible light. Any matter that falls onto a
black hole can form an external accretion disk heated by
friction , forming quasars , some of the brightest objects in
the universe. Stars passing too close to a supermassive
black hole can be shredded into streamers that shine very
brightly before being “swallowed.” If other stars are
orbiting a black hole, their orbits can be used to determine
the black hole’s mass and location. Such observations can
be used to exclude possible alternatives such as neutron
stars. In this way, astronomers have identified numerous
stellar black hole candidates in binary systems and
established that the radio source known as Sagittarius A ,
at the core of the Milky Way galaxy, contains a
supermassive black hole of about 4.3 million solar masses.