What is Black holes: Definition and 1000 Discussions
A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from 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 an enormous effect on the fate and circumstances of an object crossing it, according to general relativity it has no locally detectable features. 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 on the order of billionths of a kelvin for black holes of stellar mass, 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. The first modern solution of general relativity that would characterize a black hole was found by Karl Schwarzschild in 1916, and its interpretation as a region of space from which nothing can escape was first published by David Finkelstein in 1958. 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 discovery of neutron stars by Jocelyn Bell Burnell in 1967 sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality. The first black hole known as such was Cygnus X-1, identified by several researchers independently in 1971.Black holes of stellar mass form when very 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 (M☉) may form. There is consensus that supermassive black holes exist in the centers 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 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 shred into streamers that shine very brightly before being "swallowed." If there are other stars 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.
On 11 February 2016, the LIGO Scientific Collaboration and the Virgo collaboration announced the first direct detection of gravitational waves, which also represented the first observation of a black hole merger. As of December 2018, eleven gravitational wave events have been observed that originated from ten merging black holes (along with one binary neutron star merger). On 10 April 2019, the first direct image of a black hole and its vicinity was published, following observations made by the Event Horizon Telescope (EHT) in 2017 of the supermassive black hole in Messier 87's galactic centre. In March 2021, the EHT Collaboration presented, for the first time, a polarized-based image of the black hole which may help better reveal the forces giving rise to quasars.
As of 2021, the nearest known body thought to be a black hole is around 1500 light-years away (see List of nearest black holes). Though only a couple dozen black holes have been found so far in the Milky Way, there are thought to be hundreds of millions, most of which are solitary and do not cause emission of radiation, so would only be detectable by gravitational lensing.
this paper
Do Black Holes End up as Quark Stars ?
R.K.Thakur
(Submitted on 25 Feb 2007)
The possibility of the existence of quark stars has been discussed by several authors since 1970. Recently, it has been pointed out that two putative neutron stars, RXJ 1856.5 - 3754 in Corona Australis...
Since light is entirely incapable of slowing down, what happens when light approaches a black hole such that it's trajectory passes through the exact center of the black hole? It seems, based on what I currently know, this would mean that the gravitational force pulling on the light would be in...
For black holes to "trap" light, the light would need to enter into some sort of orbit, but it seems like that might have some odd implications with relativity. If light is revolving around the center of a black hole, that would mean the light waves/photons would constantly be changing...
Hello people,
I have a question regarding black holes. The way i understand it, black holes form in supernovas, and they occur because the gravitational pull of the stellar remnant is so great that nothing can stop it, and it basically collapses down to a singe point, virtually nothing...
Now...
So i was watching this video :
And it got me thinking... i began wondering why, when space contracts from someones frame of reference (In the video, this would be the frame of reference of the cat), why is it that the protons don't become black-holes when the space contracts?
If the density...
Do the black holes have infinite mass? If no then how can they have infinite density? Can we suppose that all the universe is orbiting a black hole (as heaviest masses bend the space time most) and loosing energy at some rate ?
A book I read says that when virtual particle-antiparticle pairs are created near a black hole then sometimes one of the particle pairs will be captured by the black hole while the other one will be freed to move away as a real particle - then this causes the black hole to lose mass and thus...
Well, do they?
Also: black holes, unlike elementary particles, have continuous distribution of rest mass, because they are free to absorb photons and gravitons of arbitrary mass, and kinetic energy of particles they capture.
If two Kerr or Newman black holes have equal spin, which happens to be...
What particles that constitute the black holes?Does normal particles constitute the black holes?
How can we calculate the ratio of types of particles in the universe(we consider known matter but not consider dark energy and dark matter)?How can we calculate the total number of particles in the...
Questions about black holes:
Various articles mention that it takes infinite amount of time to observe something pass through the event horizon.
Does this imply that the redshift observed from afar would carry on forever, that the infalling object would just become dimmer and dimmer, but never...
Hai pf,
I had a doubt? we were well known about black holes still it act as a mysterious one.
Well my question is about collision of two black holes. what happens if a highmass of black hole colloide with lowmass of black hole? Is the highmass black hole will suck the low mass black...
Black hole is considered an almost ideal black body by being a perfect black hole. But does it ideally absorb everything coming in the vicinity of its impact? Is it really possible for anybody to either ideally absorb or ideally radiate energy?
http://arxiv.org/abs/1507.05760
Higgs boson cosmology
Ian G. Moss
(Submitted on 21 Jul 2015)
The discovery of the Standard Model Higgs boson opens up a range of speculative cosmological scenarios, from the formation of structure in the early universe immediately after the big bang, to relics...
Hello,
As per the title - my name is Nick. I am soon to enter my senior year of high school. I come here partly due to recommendation of my teacher. This year, my plan is to participate in my city's annual science and engineering competition, which is connected to the Intel International...
Homework Statement
a black hole has schwarzschild radius of 15.4km what is the mass of the black hole in terms of the suns mass?Homework Equations
Rsch = 2GM/c^2
The Attempt at a Solution
I plugged values into the equation and isolated for M and it gave me a different answer. Idk how the suns...
I know that likening Black Holes to the Big Bang is common among laymen and that scientifically educated people quickly reply that they are completely different things. But I would like to understand better in which aspects are they similar and in which they are different.
If we run the...
I have always been fascinated by black holes
And I am sure that all the answers in physics are hidden in black holes...
According to Einstein nothing can go faster than the speed of light, but nothing can escape black holes not even the light.
Would it mean that the gravity resulting by a fall...
http://arxiv.org/pdf/1401.5761v1.pdf
Abstract: It has been suggested that the resolution of the information paradox for evaporating black holes is that the holes are surrounded by firewalls, bolts of outgoing radiation that would destroy any infalling observer. Such firewalls would break the...
I just watched a popular science program entitled Super Massive Black holes that proposed the idea that galaxies were formed long ago from hydrogen gas clouds whose centers collapsed to become super massive black holes that then generated star formation and ultimately the formation of galaxies...
Classical calculated with Newton the escape speed is r = 2G.M/v2. With v = c that would be the same as the Scharzschild radius calculated with GR. Does that mean that Newton laws are still valid at (or just outside) this radius?
AFAIK black holes are factual, but i can not find physical proof of the singularity, apart from Einstein's theory of general relativity, which showed that when a massive star dies, it leaves behind a small, dense remnant core. If the core's mass is more than about three times the mass of the...
What happens to the higgs field around the event horizon of a black hole, or is this currently unknown? Does the higgs field permeate inside the event horizon? Can extreme gravity affect the field in some way by changing its properties?
edguy99 submitted a new PF Insights post
https://www.physicsforums.com/insights/animating-black-holes-singularities-infinite-force-gravity/
https://www.physicsforums.com/insights/wp-content/uploads/2015/05/graviytanimation-80x80.png...
ok, hear me out on a lymph, because I'm going to either be talking crap or something that sounds crazy
either way...
my question is:
why does the phenomena of a black hole look so perfectly circular/spherical?
now here's my reasoning
spheres are the shape that takes the least energy to be...
Can someone please explain what a black hole is? I hear everyone speaking about it but have no idea what it is.
Is it something where even speed of light becomes 0? How?
Hello, I remember hearing somewhere that it is possible to calculate the event horizon, I was just wondering if this is possible and what equations are used to calculate it.
All that I've read about black holes describe something so massive it's gravity overcomes all other forces and it causes a region of spacetime to develop that no particle or electromagnetic radiation can escape from.
That explanation since it depends on mass makes no sense in regard to...
Hope this Link works. I thought this guy was great, for the layperson looking for more than the usual fluff. Might nice to give SITP some heavy "likes". Maybe they will do more.
Sorry not sure what forum this was most appropriate for...
This paper http://arxiv.org/abs/1504.00263, Assessing inflow rates in atomic cooling halos: implications for direct collapse black holes, discusses formation of direct collapse black holes in the early universe. Supermassive black holes are the only reasonable explanation for quasers in the high...
Dr. Tom Maccarone is a coauthor of the paper, “Two stellar-mass black holes in the globular cluster M22”, and is Associate Professor,Department of Physics, at Texas Tech University at Lubbock Texas. The work is discussed in a popular form at "Physicists Find Black Holes In Globular Star...
I have been thinking of how black holes help form galaxies and have come up with this idea. Now I will assume everyone who reads this knows about how black holes and quasars work.
Now if you can imagine a quasar in the beginning, ie. Without the galaxy...
"The supermassive black hole is sucking interstellar gas, but at the same time it is affecting the star-formation history of the galaxy with its powerful winds," Tombesi said. "Astrophysicists describe this process as a feedback between the central supermassive black hole and the galaxy, which...
Hello geeks!
I've reached that point in life, where I've to decide on what to study. The thing is, that I simply love the wonders and extremes of our universe, such as neutron stars, black holes etc. But the thing is, if you don't want to give lectures in a university or do research in black...
What would happen if there was a supernova explosion near a black hole ? Would it just sit there and absorb all the energy incident on it ? Or would it simply vaporize into elementary particles ? And if it does vaporize, could the remnants give us a clue as to the quantum state of matter inside...
Hello,
Always looking for answers to my questions,
I had some answers like what micro black holes
possibly created at the LHC (if it does not evaporate) would put millions or billions of years to be dangerous? I would like to know why
Sorry if I come to you
Ps : sorry for the way I did not...
Wondering if it's possible that black holes create dark matter and dark energy from the matter and energy they consume. Then, inflation might slow when supply is low. This would support author Tarō Gomi's theory that "everyone poops." What role would time dilation play if that's what's...
so i had this idea for a while now,
if you would take a black hole, and put a laser next to the event horizon, facing away from the black hole, the gravity from the black hole would pull the photons in right? I was thinking that the force that it takes must be bigger than the power from the...
This paper relies heavily of LQG self-dual black holes ; I saw an old thread here about didn't find the answer there so here's my question :
On the face of it this looks like a somewhat bizarre/exotic theoretical solution, especially with the description referring to wormholes.
However, since...
I'm curious about what others think. As I believe that you fall indefinitely in a black hole, and since you don't feel the gravity when falling, you fall until your incinerated by faster moving electromagnetic radiation falling on you. But you can only see what is above you, assuming your eyes...
Hi PF
I am reading an old Rovelli paper http://arxiv.org/abs/gr-qc/9603063
Rovelli computes the entropy of a black hole.
He says two things.
a) A state is described with an equivalence class of s-knots.
b) the entropy of a black hole can be computed by counting the number of the intersection of...
The early universe would appear to be contain more material per unit volume than now.This would then gve rise to a first generation big stars and an early develoment of supernova.
My interest lies in the inevitable momentum that would be transferred by slingshot from pairs or groups of black-...
Suppose you have a source of electron antineutrinos, and you arrange your apparatus so that a billion billion billion of them collide directly with a black hole. In principle, you could measure the change in momentum and energy from that occurrence.
Suppose you did that the next day. According...