Formation of Black Holes from Neutron Stars and White Dwarfs

[alchemist]

how is a black hole formed exactly from a neutron star or a white dwarf?? what is it?
is it a star? is it defined as a matter??
and what happens when light gets sucked into it? there ought to be an increase in energy in it right? what happens to this energy?

 

[jcsd]

When a very large star runs out of fuel it will explode as a type II supernova. It will throw the vast majority of it's mass off during the supernova, reall leaving only the core. The mass left over will collapse into either a neutron star or a black hole.

A black hole is matter as it is massive (i.e. it possesses mass) and it is a region of space from which nothing can escape (i.e. I can't think of a good concise defitnion)

Light that enters the event horizon will goto the infitely dense singulairty at the centre of the black hole. Yes this does increase the nergy of the black hole; as mass and energy are equivalent this means that the mass of the black hole will increase.

 

[relativelyslow]

a black hole is formed when a massive star (more massive than a neutron star) reaches its critical circumference (a point where the gravity overwhelms the pressure inside the star) and implodes into a black hole. as things get sucked into the black hole it does become more massive. nothing can escape a black hole; when light "tries" to it is redshifted out of existence.
im reading a book titled black holes and time warps by kip s. thorne. if your interested in them read this. its a good book. i picked it up randomly (out of random interest in black holes) so i had no previous knowledge of physics or black holes (you don't need any to understand this book).

 

[Ygmaince241]

Cool RS. I was just reading that book. However, I didn't understand something he said. He said there were extremely rare miniscule black holes, around the size of the nucleus of an atom. However, I was just watching a nova, and one of the astromoners says that a "black hole" has to be reasonably massive to be a black hole.

 

[RAD4921]

Black hole books

I read Kip Thorn's book and it was good. I recommend "About Time" by Paul Davies

 

[Nereid]

Cool RS. I was just reading that book. However, I didn't understand something he said. He said there were extremely rare miniscule black holes, around the size of the nucleus of an atom. However, I was just watching a nova, and one of the astromoners says that a "black hole" has to be reasonably massive to be a black hole.

GR, the extremely successful physics theory in which BHs are predicted, says nothing about how massive they need to be. However, the rest of science - astronomy and fundamental particle physics in particular - has a hard time coming up with realistic scenarios under BHs could occur (other than those left over from supernovae, or stellar collisions, or at the centre of large galaxies; all these are rather massive BH).

Some folk hypothesise that 'small' BH may have been created early in the history of the universe (all kinds of wild an woolly reasons), and some may still be around. They are called 'primordial black holes' (PBH).

IF (stress on if) they do exist, then some should be evaporating about now, giving off a nice burst of 'Hawking radiation', after Stephen, who first published a paper on why there should be such radiation.

AFAIK, no Hawking radiation has been observed, so PBH must be pretty 'rare'!
:surprise:

 

[idontthinkright]

I hear that the planets we are currently seeing in our night-sky is what it looked like millions of years ago.(light takes time to reach into our feeble little eyes)Does that apply to black holes too? They always say that planets are slowly vanishing from our systems,but that means it is what happened millions of years ago!So how do we know that the black holes we see in our telescopes arent actually far but nearer,or vice versa.Someone tell me,are we in imminent danger?

 

[selfAdjoint]

Not planets, but stars and galaxies. The planets of our solar system, the ones orbiting the Sun as the Earth does, are not more than hours away from us as light travels (the Sun is eight minute away).

Stars in our galaxy are a few years up to thousands of years away. Other galaxies are millions up to billions of year away. These are the things you have heard about, where what we see happened thousands or millions or billions of years ago.

So now black holes. We can't see black holes because they absorb the light that falls on them. But we can see the clouds of gas and the fast moving stars that surround them. There seems to be a big one at the center of our galaxy, but that is far away and we are moving around it on big orbit, rather than toward it.

 

[dave19903652]

With miniscule black holes wouldn't it be possible for humans to do it? Of course we don't have the technology at the mo but if you managed to create the same effect with the right atom. As the bh is smaller than the star then you could get away with something bigger... but it is technically possible

 

[Nereid]

The folk who run Google must have had so many search requests that they've set up a special entry, http://directory.google.com/Top/Science/Physics/Relativity/Black_Holes/Observations/ . Have fun!

AFAIK, there are now >10 X-ray binaries whose masses are sufficiently well determined for us to say that at least one object must be a BH. At the heart of our Milky Way galaxy is an object called Sag A*, which was thought to be massive BH quite some time ago. Gradually all other possible explanations have been ruled out by new observations, including http://curious.astro.cornell.edu/blackholes.php , of stars orbiting this BH.

BTW, that site you posted a link to ... the author can't possibly be serious; there's nary a firm prediction on it! Certainly no math, no numbers ... goodness, no matter what we find in the next decade, his stuff is so vague he could (correctly) claim new observations match perfectly. Excuse me, but that's not how I think science is done.

 

[urtalkinstupid]

Hey, I've looked at that google thingy. It only had three sites for observations that are not really persuasive to me.

http://www.owlnet.rice.edu/~spac250/steve/index.html]Black[/PLAIN] holes, if they truly exist, are very strange objects indeed. These are strange and fascinating objects, truly, but as of yet, they are still considered theoretical.

That doesn't sound too confident to me

Black holes are not yet proven and are still up for debate, but I have a couple of questions if anyone would like to answer them for me PLEASE. I'm very new to physics, but what I have studied leads me to disbelieve in a lot of well known theories. Now on to my questions about black holes.

1. Has there ever been a black hole observed that did not have a binary star orbiting it?
2. Do you believe in the concept of neutrinos? If so, could it be possible that these orbiting stars are emitting neutrinos.
3. Do Particle and Anti-particle pairs disembark at the event horizon of the black hole leading to one being pulled into the black hole and one being shot out from it? (not to sure if this is even relevant)

Like I said, I'm fairly new to physics. So far, though, what I have read is not very convincing. Heh, I'm only in High School, so please aid me in seeking out the right path in physics, if I'm not on it.

 

[Nereid]

It's quite simple, in principle: from observations of a binary object, estimate the minimum mass of each. From what we know about ordinary (and extraordinary) stars, if an object has a mass >~4 times that mass of the Sun (M_sol), then it must be either a very bright star (which would be very visible) or a BH. Why? Because if it isn't emitting copious quantities of photons (esp light, UV, IR), its core won't be hot enough to stop an ordinary matter star from collapsing. And no degenerate matter object* of that mass can avoid being crushed into a BH.

The alternative is that our understanding of physics has a huge hole in it.

The supermassive BH at the heart of galaxies aren't binaries (well, some are, e.g. Arp 220); if they were, they'd merge rather quickly (and create an event that would make a GRB look like a damp squib).

*degenerate electrons, as in a white dwarf, are highly incompressible ... until those at the highest levels start to react with protons to form neutrons (inverse beta decay), and the dwarf collapses to a neutron star, which is like a giant atomic nucleus.

 

[mee]

pbh

Would these tiny black holes be dangerous? Would they be powerful enough to eat Earth up? (insert higgs boson story here) Are black holes infinitely small or do they have a distinct diameter? If they are infinitely small, why would one have more mass than another? Does the mass of a black hole affect its size or only the distance from the singularity to the event horizon?

 

[phreak]

Would these tiny black holes be dangerous? Would they be powerful enough to eat Earth up?

Yes, and yes.

Are black holes infinitely small or do they have a distinct diameter?

The singularity of the black hole is infinitesimal (obviously), but the event horizon has a distinct diameter.

If they are infinitely small, why would one have more mass than another?

They aren't infinitely small; look above. The mass is usually referred to as the radiation/other stuff that is absorbed into the event horizon. Therefore, because the event horizon serves as the barrier of the "mass", the event horizon is usually referred to as the total mass.

(I don't have much info in this area, but from what I've read on black holes, this is accurate. In conclusion, I've probably made things worse. Sorry.)

 

[urtalkinstupid]

Bh

i still am in disbelief on the theory of black holes as well as gravity being a pull or even existing. i continue to find more sources that make logical attempts to disprove black holes existences, although they are just theories...they actually make sense and unlike the theories proposed about black holes today have baffled many scientists because of their inaccurate calculations from false mathematical attempts at explanation.

dude check out this site http://www.perceptions.couk.com/uef/nblckhls.html

im sure ill find more sites that take a shot at disproving black holes...and as it takes time to find these sites it also takes time to take an open mind to science as it has no definite way of being operated.

Excuse me, but that's not how I think science is done.

yea that's how science works...that man is questioning. that's how science works if I am not mistaken
heheh

but if you can could you provide me with links on GR and SR...and answer my question about particle/anti-particle interatcions at this phenomenons event horizon?

 

[Labguy]

but if you can could you provide me with links on GR and SR...and answer my question about particle/anti-particle interatcions at this phenomenons event horizon?

Here is just a part of an older post about virtual particle production at a BH event horizon. Both Hawking radiation and magnetic "quantum tunelling". It shows that virtual particles are produced and released at the EH by two methods. This has nothing to do with matter and energy release from an accretion disk.
________________________________________________________________
One thing that I have noticed, after reading many pages of info on "classical" Hawking Radiation (HR), is that it was conceived and most often described as in its original form as applying to a static, non-rotating, non-accreting and chargless black hole (BH) in the original Schwarzschild configuration as a simple mass-only expression of the Schwarzschild Radius (Rs) where Rs = 2GM / c^2. All of the virtual particle pair production scenarios are based on this and require one particle to "fall back" with the other escaping as a real particle causing a mass loss of the BH.

However, many other research sites and past papers have noted that it is almost impossible to form a BH with no angular momentum (spin). Even the "no hair" statement by Hawking was that a BH has only three observable properties; (1) mass, (2) angular momentum and (3) charge (usually net zero). But a lot of recent discoveries (and older theories) have added one new property that is (4) magnetic field. At first, it was thought that a magnetic field would only surround a BH that was accreting matter, but Ramon Khanna and Yakov Zeldovich have shown that all black holes will have a magnetic field. There are also the terms "Hawking Process" and “Hawking Effect” appearing, which include/combine the original HR work with work of others such as Thorn and especially Kerr (for spin) and Newman (for charge). The "Kerr-Newman" BH. (A source quote:) “David Finkelstein's Black Hole, which shows how Mass curves SpaceTime by Gravity, can be generalized to deal with Spin and Electric Charge. The generalization, called a Kerr-Newman Black Hole, was developed by Kerr (who generalized to add angular momentum J to mass M in 1963) and by Newman (who generalized to add charge e in 1965), according to the book General Relativity, by Robert Wald (Chicago 1984).

In his paper Generation and Evolution of Magnetic Fields in the Gravitomagnetic Field of a Kerr Black Hole, Ramon Khanna says: "... a rotating black hole can generate magnetic fields in an initially un-magnetized plasma. In axisymmetry a plasma battery can only generate a toroidal magnetic field, but then the coupling of the gravitomagnetic potential with toroidal magnetic fields generates poloidal magnetic fields. Even an axisymmetric self-excited dynamo is theoretically possible, i.e. Cowling's theorem does not hold close to a Kerr black hole. Due to the joint action of gravitomagnetic battery and gravitomagnetic dynamo source term, a rotating black hole will always be surrounded by poloidal and toroidal magnetic fields (probably of low field strength though). The gravitomagnetic dynamo source may generate closed poloidal magnetic field structures around the hole, which will influence the efficiency of the Blandford-Znajek mechanism whereby coupling of the gravitomagnetic potential with a magnetic field results in an electromotive force that drives currents that may extract rotational energy from a black hole.”

In June of 1971 Zeldovich announced a spinning black hole must radiate ... “a spinning metal sphere emits electromagnetic radiation ... The radiation is so weak ... that nobody has ever observed it, nor predicted it before. However, it must occur. The metal sphere will radiate when electromagnetic vacuum fluctuations tickle it. Zeldovich's mechanism by which vacuum fluctuations cause a spinning body to radiate showed a wave flowing toward a spinning object, skimming around its surface for a while, and then flowing away. The wave might be electromagnetic and the spinning body a metal sphere ... or the wave might be gravitational and the body a black hole. The incoming wave is not a "real" wave ... but rather a vacuum fluctuation. ... the wave's outer parts are in the "radiation zone" while the inner parts are in the "near zone" ... the wave's outer parts move at the speed of light ... its inner parts move more slowly than the body's surface is spinning ... the rapidly spinning body will ... accelerate ...[the inner parts of the incoming wave] ... <and this> acceleration feeds some of the body's spin energy into the wave, amplifying it. The new, amplified portion of the wave is a "real wave" with positive total energy, while the original, unamplified portion remains a vacuum fluctuation with zero total energy. Zeldovich proved that a spinning metal sphere radiates in this way; his proof was based on the laws of quantum electrodynamics.”

The quantum mechanical description of the vacuum allows for the creation of the particle/antiparticle pairs, and the electric field tends to separate the charges. If the field is strong enough, the particles tunnel through the quantum barrier and materialize as real particles. The field necessary to accomplish this feat is achieved when the work done to separated the charges by a Compton wavelength equals the energy necessary to create the particles. It should be noted that conservation of energy is not violated, as the energy it took to create the particles would be precisely equal to the decrease in the energy of the weakened electric field." .. (LABGUY NOTE: not necessarily just BH mass loss as with Hawking radiation).

Sources:
Carrol, Bradley W. and Ostlie, Dale A. An Introduction to Modern Astrophysics. Reading: Addison-Wesley, 1996.
Wald, Robert M. General Relativity. Chicago: University of Chicago, 1984.
Eisberg, R. and Resnick, R. Quantum Physics. New York: John Wiley & Sons, 1985.
Narlikar, J.V. Introduction to Cosmology. Cambridge: Cambridge University Press, 1993.
Hawking, S.W. Hawking on the Big Bang and Black Holes. New Jersey: World Scientific Publishing Co., 1993.
Hawking, S.W. A Brief History of Time. New York: Bantam Books, 1988.
Shapiro, S. and Teukolsky, S. Black Holes, White Dwarfs, and Neutron Stars - The Physics of Compact Objects. New York: John Wiley & Sons, 1983.
Thorne, Price, and Macdonald, eds. Black Holes: The Membrane Paradigm. New Haven: Yale University Press, 1986.
Wald, Robert M. General Relativity. Chicago: University of Chicago, 1984.

Web sources:
http://www.mpifr-bonn.mpg.de/gcnews/gcnews/Vol.10/rfc@gc.physics.arizona.edu_magfieldsgr.abs.shtml
http://xxx.lanl.gov/abs/astro-ph/9903091
http://www.physics.gatech.edu/people/faculty/dfinkelstein.html
http://www.innerx.net/personal/tsmith/d4d5e6hist.html
http://www.innerx.net/personal/tsmith/cdomain.html
http://www.innerx.net/personal/tsmith/BlackHole.html#KerrNewman
http://www.physics.hmc.edu/student_projects/astro62/hawking_radiation/radiation.html

 

[mee]

tiny black holes (again)

How could a black hole with an event horizon the size of an atomic nucleus contain enough mass to not let light escape. It seems to me that it would only have the mass of a softball and would thus not be any more dangerous than a softball.

 

[Nereid]

i still am in disbelief on the theory of black holes as well as gravity being a pull or even existing. i continue to find more sources that make logical attempts to disprove black holes existences, although they are just theories...they actually make sense and unlike the theories proposed about black holes today have baffled many scientists because of their inaccurate calculations from false mathematical attempts at explanation.

dude check out this site http://www.perceptions.couk.com/uef/nblckhls.html

im sure ill find more sites that take a shot at disproving black holes...and as it takes time to find these sites it also takes time to take an open mind to science as it has no definite way of being operated.

Excuse me, but that's not how I think science is done.

yea that's how science works...that man is questioning. that's how science works if I am not mistaken
heheh

but if you can could you provide me with links on GR and SR...and answer my question about particle/anti-particle interatcions at this phenomenons event horizon?

When there's two sets of material on one topic - for example, the sorts of websites you've posted links to vs 'textbook physics' on BHs - one way to make a decision as to which is worthwhile spending time studying and extending is the degree to which the two quantify things, and make specific, concrete, testable predictions.

In the present case, IMHO, it's pretty black & white - those websites are little more than handwaving and nice words; the 'textbook physics' is detailed, specific, and concrete, with plenty of testable, quantitative predictions.

Sure, those websites have lots of questions; but how many of them deal with specific, quantatitive data? You say they are 'logical attempts to disprove black holes existences''; that's certainly not science! Science is about experimental/observational support (or not) for hypotheses. The extent to which 'logic' plays a role is limited to consistency of deriving expected results, or consistency with other, well-established parts of science; none of the websites you posted are engaged in these kinds of logical exercises.

To make an absurd example: how scientific is the following (as a reason why the medicine won't work): "This medicine can't work because it's yellow"

 

[urtalkinstupid]

yes, indeed science is experimental/observational. scientists may have the experiments to prove stuff, but what they get out of those experiements sometimes don't make sense. a lot of times when scientists do computer models of gravity, the computer model doest give off results resembling our real world and how things work. yes, the sites i am providing are not textbooks, but have you ever thought about what if these textbooks are just a bunch of fabricated ideas thought up only to account for mishaps at early mathematical attempts to prove stuff? a lot of things need to be revised in physics. for one, this concept of a black hole. experiments, observations, and what have you with black holes are all just a way for scientists to explain the unknown to we people who look for answers. I am sure many scientists out there know that black holes don't exists and choose not to tell just as the parents know santa doesn't exists but deceit their children with his existence. in history it was thought that the Earth moved space through experiment and observation...that was proven wrong

but if you could provide me with some sites other than the suggestion to search on google because all sites I've found that prove stuff...dont sound too alluring

 

[Dorje]

This site:

http://www.perceptions.couk.com/

is a pseudoscience site and should not be used as a source of information.
What is pseudoscience? Try here:

http://skepdic.com/pseudosc.html

As for black hole sites that are scientific, try:

http://www.damtp.cam.ac.uk/user/gr/public/bh_home.html
http://cosmology.berkeley.edu/Education/BHfaq.html

There's an interesting story in the history of black holes. Einstein published his General Relativity equations in 1915, but it was actually Karl Schwarzschild who was the first to derive a solution to Einstein's equations. Karl imagined a type of star that was so massive that not even light could escape from it. He performed complex General Relativity calculations in between artillery calculations while he was a soldier on the front lines of World War I. His solution governed what he termed a "dark star." Karl himself didn't believe in the existence of such a strange oddity in nature, but it turns out that we do have empirical evidence (though indirect) of the existence of many black holes.

http://turnbull.dcs.st-and.ac.uk/~history/Mathematicians/Schwarzschild.html

 

[Yggdrasil]

Black holes are points in the universe where stars collapsed due to their strong gravity. Their core now has infinite density, but almost none, if any, mass.

Science is useless when it comes to a black hole. Science is the study of measurable things. Inside of a black hole, it is unmeasurable.

 

[Nereid]

yes, indeed science is experimental/observational. scientists may have the experiments to prove stuff

Hold onto these ideas, but also take time to learn what's actually being done.

It would be helpful if you could read up on what science is (and is not); you've several times used the word 'prove' in association with 'experiments'. Proof is only possible in mathematics, not science; all scientific results are tentative and qualified, proof is not possible. A more appropriate thing to say, wrt science, is something like 'there are no experimental/observational results which are inconsistent with {theory}, within its domain of applicability, to within the limits of the experimental/observational error' (note that 'experimental/observational error' has a precise meaning in science).

, but what they get out of those experiements sometimes don't make sense. a lot of times when scientists do computer models of gravity, the computer model doest give off results resembling our real world and how things work.

Can you provide some details please? Note that my request refers to specific 'computer models of gravity' which don't match specific experiments/observations (not handwaving).

yes, the sites i am providing are not textbooks, but have you ever thought about what if these textbooks are just a bunch of fabricated ideas thought up only to account for mishaps at early mathematical attempts to prove stuff?

Surely the way to test this idea is to see what the textbooks actually say, then go check for yourself! You can do this by a) working through the detailed math of the theories, to be sure that the results claimed are consistent with the theory, and b) reading up on the details of the specific experiments/observations which sought to test the theories, to be sure that the experiments/observations were done correctly, and that the results do match the theoretical predictions. At a pinch, you could also c) do your own experiments and observations.

a lot of things need to be revised in physics. for one, this concept of a black hole. experiments, observations, and what have you with black holes are all just a way for scientists to explain the unknown to we people who look for answers. I am sure many scientists out there know that black holes don't exists and choose not to tell

What really matters isn't what anyone scientist 'knows', it's how well the experimental results match the theories. As science isn't secret, you are free to 'check it out' for yourself.

 

[urtalkinstupid]

haha no more arguing here got a warning by mentor about expressing my theories in the wrong section...feel free to check out my post in theory development...ill respond to arguments there

experimental results that match theories well don't mean a thing...but that's it for now just go to my post

 

[alchemist]

how do stars implode? so what if it reaches its critical crircumference and how will this cause the star to collapse under its own gravity? I'm really new to these stuff and dun have much of any idea about this except for my utter ignorance, pls enlighten me!

 

[Aphex_Twin]

Well, if there is anyone that can answer one of theese questions, I would be forever greatful to him/her. ;)


Why does the point singularity of a black hole turn into a ring if the BH is spinning?

What would the singularity look like if the BH were spinning on 2 axes? (What if the BH were really a multi-dimensional construct and were spinning on more axes?)

What is the volume of a ring singularity (can we compute it as a function of mass and angular velocity? Is the mass of the BH distributed along the surface or inside the volume of the ring?

What are the propreties of space inside the hole of the ring and inside the ring?

 

[Phantomas]

@Aphex Twin:
Black holes can't be spinning, not noticeably anyway.

A BH shrunk to its size from a large massive star. And since it's radius got smaller and smaller it's angular momentum also got smaller. So if it's spinnig it's angular velocity is very, very small.

P.

 

[Janus]

@Aphex Twin:
Black holes can't be spinning, not noticeably anyway.

A BH shrunk to its size from a large massive star. And since it's radius got smaller and smaller it's angular momentum also got smaller. So if it's spinnig it's angular velocity is very, very small.

P.

Angular momentum is conserved. Thus as the star shrinks, its angular velocity must increase.

 

[Phantomas]

Danm, my mistake.
Laps of sudden judgement. Of course it's velocitty increases.
Sorry.

 

[Chronos]

A low mass black hole is about as dangerous as a flea on the back of an elephant. Can a flea eat the entire elephant? Er, no. The core of the earth, and sun, [both of which are even bigger than elephants] could be filled with such critters and never even feel them. Their event horizon [schwarzchild radius] is so infinitesimal, it would take them ages to eat the atoms right next to them.

But, get used to the notion that black holes are real. All the current evidence suggests they are essential to galaxy formation. They also behave entirely like any other massive body, save for the few scraps that get too close to them.

 

[meteor]

He said there were extremely rare miniscule black holes

acoording to this paper, mini black holes could be formed by the collision of cosmic rays with particles of Earth's atmosphere
http://arxiv.org/abs/hep-ph/0410190

There's also some speculation about creating mini black holes in collisions in accelerators