Black Holes: Image of Black Hole Released for First Time
by Owen Borville
April 15, 2019, updated July 22, 2024
Astronomy, Physics
The first direct images of a black hole were released this month (April 10, 2019), after observations were made by the Event Horizon Telescope in 2017 of a massive black hole. The massive black hole is at the center of the elliptical galaxy Messier 87 (M87). Scientists calculate the mass at six to seven billion times the mass of our Earth's sun. Scientists describe a black hole as an incredibly massive region of space-time where nothing can escape its gravitational pull, including particles and electromagnetic radiation such as light. No light is reflected from a black hole. The boundary of the region from which no escape is possible is called the event horizon. The theory of general relativity proposed by Albert Einstein predicts that a sufficiently compact mass can deform spacetime to form a black hole.
Black holes are believed to form when massive stars collapse at the end of their life cycle. After a black hole has formed, it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may form and there is a widespread belief among scientists that supermassive black holes exist in the centers of most galaxies.
Scientists detect the presence of a black hole from its interaction with other matter and electromagnetic radiation. The mass and location of a black hole can be detected and determined by the orbits of other stars rotating around the black hole and this information can be used to differentiate the presence of a black hole in contrast to a neutron star, which is a collapsed or exploded star that is not as massive as a black hole.
On February 11, 2016, the LIGO collaboration (Laser Interferometer Gravitational-Wave Observatory) announced the first direct detection of gravitational waves, which also represented the first observation of a black hole merger.
Black holes and their event horizons are believed to be surrounded by glowing gas and this gas is visible from the recently released images from the black hole observation. The dark central region of the black hole is not the event horizon, but is the black hole's shadow, which is the central region of emitting gas darkened by the central black hole's gravity.
The size and shape of the shadow is determined by bright gas near the event horizon, by strong gravitational lensing deflections, and by the black hole's spin. By resolving the black hole's shadow, the Event Horizon Telescope (EHT) strengthened evidence that Einstein's gravity works even in extreme regions, and gave clear evidence that the M87 galaxy has a central spinning black hole of about 6 billion solar masses.
Black holes are among the most mysterious cosmic objects, much studied but not fully understood. These objects are 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 is not a surface like Earth’s or even the Sun’s, but rather it is a boundary that contains all the matter that makes up the black hole.
There is much we don’t know about black holes, like what matter looks like inside their event horizons. However, there is a lot that scientists do know about black holes.
The nearest known black hole, called Gaia BH1, is about 1,500 light-years away. The most distant black hole detected, at the center of a galaxy called QSO J0313-1806, is around 13 billion light-years away. The most massive black hole observed, TON 618, tips the scales at 66 billion times the Sun’s mass. The lightest-known black hole is only 3.8 times the Sun’s mass. It’s paired up with a star.
Spaghettification is a real term that describes what happens when matter gets too close to a black hole as matter is squeezed horizontally and stretched vertically, resembling a noodle.
All black holes spin and the fastest-known black hole, named GRS 1915+105 – clocks in at over 1,000 rotations per second.
Large black holes at the centers of galaxies can launch particles to near light speed like a particle accelerator. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center.
If the Sun is replaced with a black hole of the same mass, the solar system would get a lot colder, but the planets would stay in their orbits, so that gravity is the same.
One type of black hole is born when massive stars run out of fuel and explode in supernovae.
Most galaxies the size of our Milky Way galaxy have very large black holes at their centers. The black hole of the Milky Way is called Sagittarius A* (pronounced ey-star), and it is 4 million times the mass of the Sun.
Supermassive black holes are so common, nearly every large galaxy has one. A black hole's mass is proportional to the mass of the host galaxy, so that, for example, a galaxy twice as massive as another would have a black hole that is also twice as massive.
Black holes don’t emit or reflect light, making them effectively invisible to telescopes. Scientists primarily detect and study them based on how they affect their surroundings:
Black holes can be surrounded by rings of gas and dust, called accretion disks, that emit light across many wavelengths, including X-rays.
A supermassive black hole’s intense gravity can cause stars to orbit around it in a particular way.
Astronomers tracked the orbits of several stars near the center of the Milky Way to prove it houses a supermassive black hole, a discovery that won the 2020 Nobel Prize.
When very massive objects accelerate through space, they create ripples in the fabric of space-time called gravitational waves. Scientists can detect some of these by the ripples’ effect on detectors.
Massive objects like black holes can bend and distort light from more distant objects. This effect, called gravitational lensing, can be used to find isolated black holes that are otherwise invisible.
Black Holes are not wormholes, in other words they do not provide shortcuts between different points in space, or portals to other dimensions or universes. Black holes do not suck in other matter. From far enough away, their gravitational effects are just like those of other objects of the same mass.
Black Holes and Galaxy Formation
Many galaxies are disc-shaped, like convex lenses, and their middle parts are known as bulges. When scientists measured the masses of several enormous black holes and those of their host galaxies’ bulges, they found a proportional relationship between the two. This means that the formation of a massive black hole and its galaxy are very closely related to each other. The galaxy and the black hole probably grew together.
Scientists are unsure whether a black hole or a galaxy came first. In recent observations, a super-massive black hole was discovered in an early-stage small galaxy. In the correlation between the mass of a black hole and that of a galaxy was that this black hole was way too big for a galaxy. It is also understood that stars were actively formed inside that galaxy. Thus, there may be some scientists who think a black hole comes first, but we cannot draw a conclusion from research on just one galaxy. There are some galaxies with no black holes, or others where a black hole has not been detected. Additionally, there are other possibilities, for example that a black hole was created when stars and galaxies collided and merged together. The research is ongoing.
Wald, R. M. (1997). "Gravitational Collapse and Cosmic Censorship". In Iyer, B. R.; Bhawal, B. Black Holes, Gravitational Radiation and the Universe. Springer. pp. 69–86. arXiv:gr-qc/9710068. doi:10.1007/978-94-017-0934-7. ISBN 978-9401709347.
Overbye, Dennis (8 June 2015). "Black Hole Hunters". NASA. Archived from the original on 9 June 2015. Retrieved 8 June 2015.
Abbott, B.P.; et al. (2016). "Observation of Gravitational Waves from a Binary Black Hole Merger". Phys. Rev. Lett. 116 (6): 061102. arXiv:1602.03837. Bibcode:2016PhRvL.116f1102A. doi:10.1103/PhysRevLett.116.061102. PMID 26918975.
Astronomy Picture of the Day, (https://apod.nasa.gov/apod/ap190411.html).
Black Holes NASA
hubblesite.org
Jaxa.jp (Kyoko Matsushita)
by Owen Borville
April 15, 2019, updated July 22, 2024
Astronomy, Physics
The first direct images of a black hole were released this month (April 10, 2019), after observations were made by the Event Horizon Telescope in 2017 of a massive black hole. The massive black hole is at the center of the elliptical galaxy Messier 87 (M87). Scientists calculate the mass at six to seven billion times the mass of our Earth's sun. Scientists describe a black hole as an incredibly massive region of space-time where nothing can escape its gravitational pull, including particles and electromagnetic radiation such as light. No light is reflected from a black hole. The boundary of the region from which no escape is possible is called the event horizon. The theory of general relativity proposed by Albert Einstein predicts that a sufficiently compact mass can deform spacetime to form a black hole.
Black holes are believed to form when massive stars collapse at the end of their life cycle. After a black hole has formed, it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may form and there is a widespread belief among scientists that supermassive black holes exist in the centers of most galaxies.
Scientists detect the presence of a black hole from its interaction with other matter and electromagnetic radiation. The mass and location of a black hole can be detected and determined by the orbits of other stars rotating around the black hole and this information can be used to differentiate the presence of a black hole in contrast to a neutron star, which is a collapsed or exploded star that is not as massive as a black hole.
On February 11, 2016, the LIGO collaboration (Laser Interferometer Gravitational-Wave Observatory) announced the first direct detection of gravitational waves, which also represented the first observation of a black hole merger.
Black holes and their event horizons are believed to be surrounded by glowing gas and this gas is visible from the recently released images from the black hole observation. The dark central region of the black hole is not the event horizon, but is the black hole's shadow, which is the central region of emitting gas darkened by the central black hole's gravity.
The size and shape of the shadow is determined by bright gas near the event horizon, by strong gravitational lensing deflections, and by the black hole's spin. By resolving the black hole's shadow, the Event Horizon Telescope (EHT) strengthened evidence that Einstein's gravity works even in extreme regions, and gave clear evidence that the M87 galaxy has a central spinning black hole of about 6 billion solar masses.
Black holes are among the most mysterious cosmic objects, much studied but not fully understood. These objects are 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 is not a surface like Earth’s or even the Sun’s, but rather it is a boundary that contains all the matter that makes up the black hole.
There is much we don’t know about black holes, like what matter looks like inside their event horizons. However, there is a lot that scientists do know about black holes.
The nearest known black hole, called Gaia BH1, is about 1,500 light-years away. The most distant black hole detected, at the center of a galaxy called QSO J0313-1806, is around 13 billion light-years away. The most massive black hole observed, TON 618, tips the scales at 66 billion times the Sun’s mass. The lightest-known black hole is only 3.8 times the Sun’s mass. It’s paired up with a star.
Spaghettification is a real term that describes what happens when matter gets too close to a black hole as matter is squeezed horizontally and stretched vertically, resembling a noodle.
All black holes spin and the fastest-known black hole, named GRS 1915+105 – clocks in at over 1,000 rotations per second.
Large black holes at the centers of galaxies can launch particles to near light speed like a particle accelerator. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center.
If the Sun is replaced with a black hole of the same mass, the solar system would get a lot colder, but the planets would stay in their orbits, so that gravity is the same.
One type of black hole is born when massive stars run out of fuel and explode in supernovae.
Most galaxies the size of our Milky Way galaxy have very large black holes at their centers. The black hole of the Milky Way is called Sagittarius A* (pronounced ey-star), and it is 4 million times the mass of the Sun.
Supermassive black holes are so common, nearly every large galaxy has one. A black hole's mass is proportional to the mass of the host galaxy, so that, for example, a galaxy twice as massive as another would have a black hole that is also twice as massive.
Black holes don’t emit or reflect light, making them effectively invisible to telescopes. Scientists primarily detect and study them based on how they affect their surroundings:
Black holes can be surrounded by rings of gas and dust, called accretion disks, that emit light across many wavelengths, including X-rays.
A supermassive black hole’s intense gravity can cause stars to orbit around it in a particular way.
Astronomers tracked the orbits of several stars near the center of the Milky Way to prove it houses a supermassive black hole, a discovery that won the 2020 Nobel Prize.
When very massive objects accelerate through space, they create ripples in the fabric of space-time called gravitational waves. Scientists can detect some of these by the ripples’ effect on detectors.
Massive objects like black holes can bend and distort light from more distant objects. This effect, called gravitational lensing, can be used to find isolated black holes that are otherwise invisible.
Black Holes are not wormholes, in other words they do not provide shortcuts between different points in space, or portals to other dimensions or universes. Black holes do not suck in other matter. From far enough away, their gravitational effects are just like those of other objects of the same mass.
Black Holes and Galaxy Formation
Many galaxies are disc-shaped, like convex lenses, and their middle parts are known as bulges. When scientists measured the masses of several enormous black holes and those of their host galaxies’ bulges, they found a proportional relationship between the two. This means that the formation of a massive black hole and its galaxy are very closely related to each other. The galaxy and the black hole probably grew together.
Scientists are unsure whether a black hole or a galaxy came first. In recent observations, a super-massive black hole was discovered in an early-stage small galaxy. In the correlation between the mass of a black hole and that of a galaxy was that this black hole was way too big for a galaxy. It is also understood that stars were actively formed inside that galaxy. Thus, there may be some scientists who think a black hole comes first, but we cannot draw a conclusion from research on just one galaxy. There are some galaxies with no black holes, or others where a black hole has not been detected. Additionally, there are other possibilities, for example that a black hole was created when stars and galaxies collided and merged together. The research is ongoing.
Wald, R. M. (1997). "Gravitational Collapse and Cosmic Censorship". In Iyer, B. R.; Bhawal, B. Black Holes, Gravitational Radiation and the Universe. Springer. pp. 69–86. arXiv:gr-qc/9710068. doi:10.1007/978-94-017-0934-7. ISBN 978-9401709347.
Overbye, Dennis (8 June 2015). "Black Hole Hunters". NASA. Archived from the original on 9 June 2015. Retrieved 8 June 2015.
Abbott, B.P.; et al. (2016). "Observation of Gravitational Waves from a Binary Black Hole Merger". Phys. Rev. Lett. 116 (6): 061102. arXiv:1602.03837. Bibcode:2016PhRvL.116f1102A. doi:10.1103/PhysRevLett.116.061102. PMID 26918975.
Astronomy Picture of the Day, (https://apod.nasa.gov/apod/ap190411.html).
Black Holes NASA
hubblesite.org
Jaxa.jp (Kyoko Matsushita)