Black Hole

A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space.

This can happen when a star is dying.

Black holes are found throughout the universe, even in the Milky Way.

The idea of ​​what we currently call a black hole had already been enunciated in 1783.

But, scientists rejected it, because at that time it was believed that light had no mass, so it could not be attracted by any body, no matter how dense it was.

When Albert Einstein developed general relativity in 1915, he showed that light was influenced by gravitational interaction and that a very massive body could exert attraction on photons of light.

John Wheeler coined the term black hole

The term “black hole” was coined by the American theoretical physicist John Wheeler (1911-2008).

John Wheeler
John Wheeler American with a very productive scientific life. Credit: web “phy.princeton.edu/department/history/faculty-history/john-wheeler”.

He chose this name as a metaphor for the sinister possibility of the disintegration of stars and planets.

John Wheeeler’s friendship with Niels Bohr

When Niels Bohr, father of the quantum revolution, came to the United States in 1939, John Wheeler was a young physics professor at the prestigious Princeton University.

The passion for science led to a great friendship between them, which lasted throughout their lives.

Bohr brought the alarming news to the United States that the Germans had succeeded in fissioning the atom.

Niels Bohr and John Wheeler began to study tirelessly until they were able to devise a theory about nuclear fission.

Both worked on the Manhattan project for the manufacture of the atomic bomb in the USA.

After World War II, Wheeler was responsible for the education of several generations of scientists, including Richard Feyman and Hugh Everett.

Stephen Hawking popularized the name black hole

The famous astrophysicist Stephen Hawking popularized the name, with the publication of the book entitled “Black holes and the history of time“.

In this work, Hawking explains that when the internal energy of a giant star is completely extinguished, the enormous mass of the star is subjected to its own force of gravity, which is exerted without counterweight on itself.

Black hole
Ilustration of a black hole. Credit: ESO, ESA/Hubble, M.Kornmesser/N.Bartmann; Labels: NASA/CXC .

The lead author of the result, which used data from both NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton, is Giovanni Minuitti of the Center for Astrobiology (CAB, CSIC-INTA) in Spain. Web: “chandra.harvard.edu/blog/node/737”

This enormous gravitational force causes the stellar mass to concentrate in a small volume.

In this way, the red giant star becomes a white dwarf star.

This process of gravitational self-attraction gives rise to a body so dense and possessing such a gigantic force of gravity that not even light has a sufficient escape velocity to leave this body.

Such body is therefore invisible from the outside.

Characteristics of a black hole

One of the likely characteristics of a black hole is that anything, including space that is located in the zone of attraction caused by a black hole, would accelerate to extreme speed like in a vortex and everything would be directed towards the center of the black hole. .

In 1963, Roy Kerr had shown that in a four-dimensional spacetime, all black holes must have a quasi-spherical geometry determined by three parameters:

  • their mass M,
  • their total electric charge e, and
  • their angular momentum L.

In the 1970s, Stephen Hawking and Ellis proved several important theorems about the occurrence and geometry of black holes.

The hypothesis of the existence of black holes gained strength with the scientific and experimental advances that led to the discovery of pulsars.

Black hole
The Crab Nebula, which contains the Crab Pulsar (the red star in the center). Credit: NASA/CXC/ASU/J. Hester et alter.

Image combines optical data from Hubble (in red) and X-ray images from Chandra (in blue).

The existence of black holes is supported by astronomical observations, especially through the X-rays emitted by binary stars and active galaxies.

The so-called supermassive black holes are those that have masses several million times the mass of the Sun.

They are formed during the process that gives rise to the spherical components of galaxies.

Findings after 1995

In 1995, a team of researchers from UCLA (University of California) demonstrated, through computer simulation, the possibility of the existence of supermassive black holes in the nucleus of galaxies.

According to an article published in The Astrophysical Journal, in August 2009, from the European Southern Observatory in Chile, a team of German astronomers discovered that, in the center of the Milky Way, there is a black hole that is four million times heavier than the Sun.

Milky Way
An artist’s rendering shows the Milky Way where a supermassive black hole lies at the center. Credit: Spitzer Space Telescope/NASA/JPL-Caltech/R. Hurt.

A dozen smaller black holes have now been detected, and a new study suggests the monster is surrounded by about 10,000.

This discovery was made by following the movement of 28 stars revolving around the center of the Milky Way for 16 years.

The stellar orbits at the galactic center show that the central mass concentration of four million solar masses must, without a doubt, be a black hole.

Researchers at the Max Planck Institute for Extraterrestrial Physics, in Germany, assured that this black hole is 27,000 light years from Earth.

Until today it is impossible to describe what happens inside a black hole; one can only imagine, suppose, and observe its effects on matter and energy in outer zones.

The whole theory is under review. It is clear that until more advanced physics is available, it will not be possible to really explain the nature of this phenomenon.

In December 2008, a team from the Max Planck Institute confirmed the existence of such a supermassive black hole in the center of the Milky Way.

It is estimated that the mass of this black hole is equivalent to the mass of 4 million suns and that it is located at a distance of 27,000 light years from Earth.

Despite the perception that black holes are destructive, it is assumed that by condensing matter around them, they partly cause the constitution of galaxies and the formation of new stars.

The Swedish Academy of Sciences awarded the “Nobel for Astronomy 2012” to the German astronomer Reinhard Genzel and the American Andrea Ghez.

According to the Swedish Academy, this award recognizes “observations of stars orbiting around the galactic center, indicating the presence of a supermassive black hole“.