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Deepak Kapur
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1. I repeat, 'what is the size of a black hole'.
2. Is there anything denser/smaller than a black hole?
2. Is there anything denser/smaller than a black hole?
silentbob14 said:2. A singularity at the moment of the big bang was smaller than any of the black hole singularities.
silentbob14 said:Shouldn't an object, which has a mass have a volume (bigger than zero)?
Deepak Kapur said:2. Is there anything denser/smaller than a black hole?
nicksauce said:This question seems to assume that all black holes have the same size, which is false. At a given mass, a black hole would be the smallest, densest thing of that mass.
nicksauce said:1. A black hole of mass M has radius R = 2GM/c^2
AUK 1138 said:this is the size of the Schwarzschild radius, not the size of the black hole. by your definition, the black hole is a rather large object. when in reality, a black hole operates more like a point particle, ie a singularity.
Deepak Kapur said:1. I repeat, 'what is the size of a black hole'.
What is a black hole?
A black hole is a concentration of matter so dense that not even light can escape its gravitational pull.
What is a supermassive black hole?
Black holes come in many sizes. Astronomers believe that a “supermassive” black hole, with a mass of about 4 million Suns, lies at the center of the Milky Way galaxy. NRAO telescopes offer the best prospect for actually imaging such a supermassive black hole.
More generally, a supermassive black hole has a mass of several hundred thousand to more than ten billion solar masses. The central region of virtually every galaxy is thought to contain an object of this type. The primary evidence for supermassive black holes comes from optical and radio observations which show a sharp rise in the velocities of stars or gas clouds orbiting the centers of galaxies. High orbital velocities mean that something massive is creating a powerful gravitational field that is accelerating the stars. Additionally, X-ray observations indicate that a large amount of energy is produced in the centers of many galaxies, presumably by material falling into the accretion disk that surrounds the central black hole.
How do supermassive black holes form?
One theory is that an individual star-like black hole forms and swallows up enormous amounts of matter over the course of millions of years to produce a supermassive black hole. Another possibility is that a cluster of star-like black holes forms and eventually merges into a single, supermassive black hole. Or, a single large gas cloud could collapse to form a supermassive black hole.
Recent research suggests that galaxies and their central black holes do not grow steadily, but in fits and starts. In the beginning of a growth cycle, the galaxy and its central black hole accumulate matter. The energy generated by the jets that accompany the growth of the supermassive black hole eventually brings the in-fall of matter and the growth of the galaxy to a halt. The activity around the central black hole then ceases because of the lack of a steady supply of matter, and the jets disappear. Millions of years later the hot gas around the galaxy cools and resumes falling into the galaxy, initiating a new season of growth.
[Read on . . .]
http://www.nrao.edu/index.php/learn/science/blackholes
ViewsofMars said:Hello Deepak Kapur (OP), I think that The National Radio Astronomy Observatory should be of help to you in your search. It is a 'facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.' that means it's "A" ok!
Deepak Kapur said:How is it possible when the volume is zero in either case?and finally Nabeshin put it to rest. Don't take this the wrong way, but how is a puff-piece from NRAO clarifying this? A supermassive BH is still conforming to its Schwarzschild Radius, and then related phenomenon such as the Event Horizon, and Ergoregion (and accretion disc if you like) would be the "rest". I think Nabeshin already took us past the approximation offered in that article.
Perhaps I'm missing some element you are trying to communicate?
Nature 464, 380-383 (18 March 2010)
Dust-free quasars in the early Universe
Linhua Jiang1, Xiaohui Fan1,2, W. N. Brandt3, Chris L. Carilli4, Eiichi Egami1, Dean C. Hines5, Jaron D. Kurk2,6, Gordon T. Richards7, Yue Shen8, Michael A. Strauss9, Marianne Vestergaard1,10 & Fabian Walter2
[...]
The most distant quasars known, at redshifts z ≈ 6, generally have properties indistinguishable from those of lower-redshift quasars in the rest-frame ultraviolet/optical and X-ray bands. This puzzling result suggests that these distant quasars are evolved objects even though the Universe was only seven per cent of its current age at these redshifts. Recently one z ≈ 6 quasar was shown not to have any detectable emission from hot dust4, but it was unclear whether that indicated different hot-dust properties at high redshift or if it is simply an outlier. Here we report the discovery of a second quasar without hot-dust emission in a sample of 21 z ≈ 6 quasars. Such apparently hot-dust-free quasars have no counterparts at low redshift. Moreover, we demonstrate that the hot-dust abundance in the 21 quasars builds up in tandem with the growth of the central black hole, whereas at low redshift it is almost independent of the black hole mass. Thus z ≈ 6 quasars are indeed at an early evolutionary stage, with rapid mass accretion and dust formation. The two hot-dust-free quasars are likely to be first-generation quasars born in dust-free environments and are too young to have formed a detectable amount of hot dust around them.
[Read on . . .]
http://www.nature.com/nature/journal/v464/n7287/full/nature08877.html
The size of a black hole is determined by its event horizon, which is the point of no return for anything that enters the black hole. The event horizon is typically measured in terms of its radius, with the average radius of a stellar black hole being around 10 kilometers.
Yes, black holes can vary in size depending on their mass. The more massive a black hole is, the larger its event horizon and overall size will be. For example, supermassive black holes at the center of galaxies can have event horizons that extend for thousands of light years.
The size of a black hole is directly related to its gravitational pull. The larger the size, the stronger the gravitational pull. This is due to the fact that the more massive a black hole is, the more space it warps around it, creating a stronger gravitational force.
No, it is not possible for a black hole to have a size of zero. All black holes have a singularity at their center, which is a point of infinite density and zero volume. This means that even if a black hole has a very small event horizon, it still has a finite size due to the singularity.
Yes, the size of a black hole can change over time. This can happen through a process called accretion, where a black hole gains mass from the surrounding matter, causing its event horizon to grow. Black holes can also lose mass through Hawking radiation, which can cause their event horizon to shrink over time.