Black holes

Extracted Attributes

• Field

  Astrophysics

• Types

  Stellar black holes, Supermassive black holes

• Property

  Acts like an ideal black body

• Key Concept

  Event Horizon

• Growth Mechanisms

  Absorbing surrounding matter, merging with other black holes, direct collapse of gas clouds (for supermassive black holes)

• Prediction Source

  Albert Einstein's theory of general relativity

• Quantum Prediction

  Emit Hawking radiation

• Mass of Sagittarius A*

  Approximately 4.3 million solar masses

• Observational Evidence

  Interactions with surrounding matter, electromagnetic radiation, accretion disks, orbits of nearby stars

• Example Stellar Black Hole

  Cygnus X-1

• Primary Formation Mechanism

  Collapse of massive stars

• Example Supermassive Black Hole

  Sagittarius A* (at the center of the Milky Way)

• Hawking Radiation Temperature (stellar black holes)

  Order of billionths of a kelvin

Timeline

• Objects whose gravitational fields are too strong for light to escape were first considered by John Michell and Pierre-Simon Laplace. (Source: Wikipedia)

  1700-01-01

• John Michell argues that a star 500 times wider than the Sun would have gravity strong enough to prevent light escape, calling them 'dark stars'. (Source: ESA web search)

  1784-01-01

• Predicted by Albert Einstein through his general theory of relativity. (Source: ESA web search)

  1915-01-01

• Karl Schwarzschild finds the first modern solution of general relativity that would characterize a black hole (Schwarzschild metric). (Source: Wikipedia)

  1916-01-01

• David Finkelstein first publishes the interpretation of 'black hole' as a region of space from which nothing can escape. (Source: Wikipedia)

  1958-01-01

• Theoretical work shows black holes were a generic prediction of general relativity. (Source: Wikipedia)

  1960-01-01

• Cygnus X-1 identified as the first black hole. (Source: Summary, Wikipedia)

  1971-01-01

Black hole

A black hole is an astronomical body so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. The boundary of no escape is called the event horizon. In general relativity, a black hole's event horizon seals an object's fate but produces no locally detectable change when crossed. 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. Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. In 1916, Karl Schwarzschild found the first modern solution of general relativity that would characterise a black hole. Due to his influential research, the Schwarzschild metric is named after him. David Finkelstein, in 1958, first published the interpretation of "black hole" as a region of space from which nothing can escape. Black holes were long considered a mathematical curiosity; it was not until the 1960s that theoretical work showed they were a generic prediction of general relativity. The first black hole known was Cygnus X-1, identified by several researchers independently in 1971. Black holes typically form when massive stars collapse at the end of their life cycle. After a black hole has formed, it can grow by absorbing mass from its surroundings. Supermassive black holes of millions of solar masses may form by absorbing other stars and merging with other black holes, or via direct collapse of gas clouds. There is consensus that supermassive black holes exist in the centres of most galaxies. The presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as visible light. Matter falling toward a black hole can form an accretion disk of infalling plasma, heated by friction and emitting light. In extreme cases, this creates a quasar, 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.

Web Search Results

• Black hole

  A black hole is an astronomical body so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. The boundary "Boundary (topology)") of no escape is called the event horizon. In general relativity, a black hole's event horizon seals an object's fate but produces no locally detectable change when crossed. In many ways, a black hole acts like an ideal black body, as it [...] For other uses, see Black hole (disambiguation) "Black hole (disambiguation)"). An image of the core region of Messier 87, a supermassive black hole, processed from a sparse array of radio telescopes known as the EHT with colors indicating brightness temperature. [...] Black holes typically form when massive stars collapse at the end of their life cycle. After a black hole has formed, it can grow by absorbing mass from its surroundings. Supermassive black holes of millions of solar masses may form by absorbing other stars and merging with other black holes, or via direct collapse of gas clouds. There is consensus that supermassive black holes exist in the centres of most galaxies.

• Black holes, explained - UChicago News - The University of Chicago

  UChicago Explainer Series # Black holes, explained Black holes are regions in space where an enormous amount of mass is packed into a tiny volume. This creates a gravitational pull so strong that not even light can escape. They are created when giant stars collapse, and perhaps by other methods that are still unknown. Black holes fascinate both the public and scientists—they push the limits of our understanding about matter, space and time. [...] Black holes are created when massive stars collapse at the end of their lives (and perhaps under other circumstances that we don’t know about yet). One of the first steps toward the discovery of black holes was made by University of Chicago professor Subrahmanyan Chandrasekhar, when he realized that massive stars would have to collapse after they ran out of fuel for the fusion reactions which keep them hot and bright. [...] Black holes are kind of like a playground for physicists. “They are literally made out of space and time,” said Prof. Holz. Because they are so extreme, they are the perfect place to test the limits of the rules of the universe.

• ESA - Black holes

  A black hole is an extremely dense object whose gravity is so strong that nothing, not even light, can escape it. Every object in space has an 'escape velocity': the minimum speed at which something must move to escape the object's gravitational field. On the surface of Earth, the escape velocity is about 11 kilometres per second, meaning that anything leaving our planet must travel faster than this to break free of Earth's gravitational pull. [...] Black holes were predicted by Albert Einstein through his general theory of relativity in 1915, but the idea of a black hole is actually much older. In 1784 John Michell argued that if light was indeed a stream of particles (as Isaac Newton’s theory suggested), then it should be influenced by gravity. Following this assumption, Michell predicted that a star 500 times wider than the Sun would have such a strong gravitational field that even light could not escape. He called these objects ‘dark

• What Is a Black Hole? How They Form in Space? - YouTube

  ### Description 32198 views Posted: 16 May 2022 A black hole is a celestial body or simply a place in space where the gravitational pull is so high that nothing, not even light can escape it. This is why it's completely black, and hence it's called a black hole. A black hole's “surface,” called its event horizon, defines the boundary where the velocity needed to escape exceeds the speed of light. [...] 38 comments ### Transcript: Intro Black holes are one of the few natural phenomena that were mathematically predicted first and then observed later. They were first predicted in 1780s by natural philosopher Jon Michell who suggested that the gravity of a sufficiently dense star could be so great that even light emitted by it would be unable to escape its pull. The discovery in Cygnus relieved the astronomers because otherwise they would’ve [...] A black hole is not just empty space; in fact, it’s a great deal of amount packed into a very small area. Think of a star which is 10 times more massive than our is squeezed into a sphere which has the diameter equal to the size of New York city. The result will be a celestial object whose gravitational field is so strong that nothing, not even light, can escape it. This is why black holes are named so, because they are pitch black!

• Black Hole Basics - NASA Science

  Black holes are among the most mysterious cosmic objects, much studied but not fully understood. These objects aren’t really holes. They’re huge concentrations of matter packed into very tiny spaces. A black hole is so dense that gravity just beneath its surface, the event horizon, is strong enough that nothing – not even light – can escape. The event horizon isn’t a surface like Earth’s or even the Sun’s. It’s a boundary that contains all the matter that makes up the black hole.