×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Short Gamma-ray Bursts Traced to Colliding Stars

samzenpus posted more than 8 years ago | from the stars-smash dept.

Space 135

Astervitude writes "Collisions of the cosmic kind could be the source of one of nature's most lethal explosions. Astronomers have traced the origin of short-duration gamma-ray bursts, or GRBs, to the merger of neutron stars or other dense bodies. Space.com has a report on the scientific detective work that led to the solution of what has been described as a 35-year-old mystery. "Our observations do not prove the coalescence model, but we surely have found a lady with a smoking gun next to a dead body," said Shri Kulkarni, one of over two dozen astronomers who discovered and investigated two short-duration bursts that took place last May and July. Unlike short-duration GRBs, long-duration GRBs are believed to be produced when extremely massive stars collapse and explode as supernovas."

cancel ×
This is a preview of your comment

No Comment Title Entered

Anonymous Coward 1 minute ago

No Comment Entered

135 comments

i love you (-1, Offtopic)

Anonymous Coward | more than 8 years ago | (#13727680)

i love you

The Science Channel (4, Interesting)

Namronorman (901664) | more than 8 years ago | (#13727689)

The Science Channel has recently (by coincidence?) been showing a lot of programs talking about stars and the sun, and a very common topic has been Gamma Ray Bursts.

I just think it's weird how some things seem like a trend some times.

The idea of neutron stars colliding is a very old theory but this seems to shed new light on the possibility of it being the main cause.

Re:The Science Channel (2, Interesting)

Zindagi (875849) | more than 8 years ago | (#13727873)

One of the reasons that comes to mind is the launch of a new satellite for observing GRBs SWIFT [nasa.gov]. And the fact that GRB's are intrinsically intriguing - being the huge balls of energy (if you will) in the Universe

Re:The Science Channel (0)

Anonymous Coward | more than 8 years ago | (#13728207)

I've noticed this happen a lot too, but IMHO, it is purely coincidence - during your life there is so much opportunity for coincidence like this, so even with a tiny probability of it just randomly happening, it's bound to occur given enough time.

article is slightly misleading... (0)

eobanb (823187) | more than 8 years ago | (#13727691)

It should be noted that ordinary fusion reaction stars (giants, main sequence stars, and dwarfs) don't collide, because they're massive enough not to change direction easily from their usual trajectories (away from each other, as the universe expands), but not massive enough to actually have the gravitational force to be drawn towards other stars. I can only suppose that neutron stars have sufficient mass to bring about such a collision.

Re:article is slightly misleading... (2, Informative)

eobanb (823187) | more than 8 years ago | (#13727700)

Let me add on to this and also mention that when two stars do get close to each other they tend to fall into orbit around each other instead of just colliding, obviously. In that case, you have another star in close enough proximity to keep the star in an acceleration curve.

Re:article is slightly misleading... (1)

Lucractius (649116) | more than 8 years ago | (#13728054)

let me just add that massive bodies of all kinds are attacted towards eachother. so your point about them drifting apart is rather misleading. the expantion of the universe on a interstellar scale is not significant compared to the gravitational bonds of the galactic core that the stars orbit.

It is quite reasonable that stars can colide on their orbits around the galactic core. takes about 200 million years for the solar system to orbit the galactic core. 2 stars could have intersecting orbits and consequently collide at some point.

thats just the explanation for big ones. stars regularly form binary pairs, so all of this collision stuff is fairly regular orbital mechanics. Orbits decay. End of the argument.

Re:article is slightly misleading... (4, Informative)

Capt'n Hector (650760) | more than 8 years ago | (#13727751)

Um... ok. 1) Mass has nothing to do with a star's ability to collide. 2) the universe's expansion only effects entire galaxies over extremely long distances. Individual stars in galaxies are not affected by this. In fact, they are drawn towards each other as seen in binary+ systems. This is where colliding neutron stars comes from. We need a binary system where both stars are of sufficient size to go supernova and create two neutron stars. Now we have two neutron stars orbiting each other. While the following can be derived directly from Einstein's equations in a single college lecture, it's rather too complex to detail in a slashdot comment... essentially these two neutron stars spiral inward towards each other because with each orbit they loose enough orbital energy due to gravitational waves (energy given off by a gravitational wave is inversely proportional to orbital period and proportional to mass - or something like that) It turns out this energy is of an appreciable amount so that eventially these stars will collide in a reasonable amount of time. So yeah.

Don't they have to be damn close? (1)

Quadraginta (902985) | more than 8 years ago | (#13727834)

I'd think the loss from gravitational waves would be miniscule unless they were very close to each other. Which, granted, NS can do, being small and dense and all -- but how do they get that close to begin with?? Are we thinking some hideously close binary where the two stars start out mere dozens of AU apart? Inquiring minds want to know...

Re:Don't they have to be damn close? (1)

Hays (409837) | more than 8 years ago | (#13727879)

I'm no expert, but one can imagine how it is possible for them to end up as two neutron stars relativly close to each other such that gravitational drag can pull them together within the lifespan of the universe-

First, they don't go supernova at the same time. One becomes a neutron star, and then the other. When the relationship is asymmetrical, one neutron one star, I think they have more interaction with each other. No shockwave keeping most of their materials apart. Instead material will be spiraling onto the neutron star from the other one, and that probably has the effect of imparting drag and bringing them together. Also I don't think the supernovae necessarily impart their forces symmetrically. They might have the effect of countering a lot of the momentum of one of the stars (or rather ejected material goes one direction, neutron core goes the other)

This is somewhat conjecture. But your point is a good one, I think. Surely their is some minimum distance at which large, supernova proned binary stars can form. And surely gravitational drag is a very slow phenomena.

Re:Don't they have to be damn close? (1)

eobanb (823187) | more than 8 years ago | (#13727944)

I don't see how gravitational drag could really have anything to do with it. The way I could concieve two neutron stars coming together would be stars A and B travelling on roughly parallel paths through the galaxy, and gravity pulls them together. Simple as that. If stars are orbiting each other, it's totally different. If you have two ball bearings on a frictionless plane that curves up on two sides, with the lowest area being a line down the centre, the bearings are going to accelerate to that low point. On the other hand, if you have some sort of plane with a single point that's the lowest (instead of a line), then the balls are just going to revolve around this point forever. The only way they wouldn't is if they had absolutely zero velocity to start with. Then they would just be pulled into the point, and that would be that. But neutron stars tend to have some sort of momentum, and they're not so likely to just happen to be heading straight into one another. Ultimately it just seems really unlikely and bizarre, but I guess it's theoretically possible, just more probable than ordinary stars colliding. It's like having a bunch of magnets floating about in a zero-G room versus ordinary objects.

Re:Don't they have to be damn close? (2, Informative)

The Master Control P (655590) | more than 8 years ago | (#13728029)

Neutron stars and other things like them do wierd things: Objects that dense and massive, spiraling around each other that fast, create gravitational waves [nasa.gov] like moving a stick through a pond. Energy is needed to create gravity waves, and it comes from the orbital motion of the neutron stars. Their existing orbits slow down; They fall closer and orbit even faster, generating more gravity waves than before.

Re:Don't they have to be damn close? (0)

Anonymous Coward | more than 8 years ago | (#13731648)

ejected material goes one direction, neutron core goes the other
When a bomb goes off, the material inside the bomb does not move in one direction and the explosion in another. The bomb, like a star going supernova, explodes more or less evenly outwards; if it did not, and if the core did move, it would likely never collapse to a neutron star--an object in motion will remain in motion, and as the core moves away from the cloud it loses mass and thus gravitational attraction.

Re:article is slightly misleading... (3, Funny)

WalterGR (106787) | more than 8 years ago | (#13728101)

...it's rather too complex to detail in a slashdot comment.

Dude - never talk about the space in which you would write an explanation. That's like the ultimate jinx. The last time a guy did that, it took the rest of the world 357 years to figure it out.

;)

Re:article is slightly misleading... (0)

Anonymous Coward | more than 8 years ago | (#13727780)

Is that where flux capacitors are born, when two "ordinary fusion reaction stars" collide? GREAT SCOTT!!!

You're right, they're massive enough. (3, Interesting)

Spy der Mann (805235) | more than 8 years ago | (#13727785)

I can only suppose that neutron stars have sufficient mass to bring about such a collision.

Actually, that's an understatement.

According to the wikipedia [wikipedia.org], a neutron star is about 1.5 times massive as the sun... and that would be about 1.5 × 2x10^30 kg = 3x10^30kg, but ONLY 12 miles in diameter. One can just imagine the gravitational force these things have.

I'd appreciate it if someone made calculation: If two neutron stars are say, 10,000 km far from each other, what will be the acceleration? (remember, the greater the mass, the greater the acceleration). And what speed will they have when they collide? Finally, what will be the kinetic force at the time of impact?

Re:You're right, they're massive enough. (1)

pomo monster (873962) | more than 8 years ago | (#13727881)

"...a neutron star is about 1.5 times massive as the sun ... but ONLY 12 miles in diameter. One can just imagine the gravitational force these things have."

Sure, so about 1.5 times the gravitational force of the sun? ;-)

Re:You're right, they're massive enough. (1)

njchick (611256) | more than 8 years ago | (#13727930)

At the distance equal the solar raduis. Much higher on the surface.

Re:You're right, they're massive enough. (1)

Anonymous Coward | more than 8 years ago | (#13727940)

I'm sure he means surface gravity. A neutron star has a surface gravity of about 10^11 times greater than Earth's. It also has a magnetic field strong enough to disrupt atomic nuclei. source [umd.edu]

Re:You're right, they're massive enough. (1)

theorl21 (909087) | more than 8 years ago | (#13727985)

Its gravitational force would be much greater than our sun's. If so much mass is compressed in a 12 mile in diameter area, then imagine how much a simple teaspoon of matter would end up weighing in this star. The way I understand it, the more tightly compact mass is, the greater its gravitational effect within an ever decreasing sorrounding area.

Re:You're right, they're massive enough. (1)

m50d (797211) | more than 8 years ago | (#13728121)

Its gravitational force would be much greater than our sun's. If so much mass is compressed in a 12 mile in diameter area, then imagine how much a simple teaspoon of matter would end up weighing in this star. The way I understand it, the more tightly compact mass is, the greater its gravitational effect within an ever decreasing sorrounding area.

The same amount of mass will always produce the same amount of force no matter how compressed. The difference is that you're much closer to the center on the surface, and since gravity follows an inverse-square law the force will be a helluva lot more on the surface of such a dense object than that of a huge ball with the same mass. But the force (say) 10000km from the centre will be the same.

Re:You're right, they're massive enough. (1)

SimilarityEngine (892055) | more than 8 years ago | (#13728248)

Diameter of sun is approx 1,400,000 km. So the gravitational field strength at 10,000 km from the centre of the sun will be considerably less than that 10,000 km from the centre of a neutron star. Also it'd be a bit warm - T-shirt and shorts weather, I think.

;-)

Re:You're right, they're massive enough. (1)

Ihlosi (895663) | more than 8 years ago | (#13728269)

Also it'd be a bit warm - T-shirt and shorts weather, I think.



Don't forget the sunscreen, either. Preferably with a LPF that ends with "e[really large number]"

Re:You're right, they're massive enough. (1)

layer3switch (783864) | more than 8 years ago | (#13727939)

Matter of fact, neutron star's gravitational force according to Thacker Nuclear Binding Theory of Gravity, once the nuclei are bound very tightly together, become very weak. So it wouldn't be 1.5 times of the Sun even though mass is about equal.

Re:You're right, they're massive enough. (1)

Decaff (42676) | more than 8 years ago | (#13733285)

Matter of fact, neutron star's gravitational force according to Thacker Nuclear Binding Theory of Gravity, once the nuclei are bound very tightly together, become very weak. So it wouldn't be 1.5 times of the Sun even though mass is about equal.

This theory is utter nonsense. If the gravity was weak, the nucleii would not be bound together!

Proof that this theory is nonsense is that very precise observations of the orbits of binary pulsars have confirmed Einstein's theory of gravity.

Re:You're right, they're massive enough. (3, Informative)

The Master Control P (655590) | more than 8 years ago | (#13728000)

If two neutron stars are say, 10,000 km far from each other, what will be the acceleration? (remember, the greater the mass, the greater the acceleration).
Well, the gravitational acceleration from a point mass at a given distance is MG/R^2 (force computed by plugging a second mass in on top). 3 * 10^30 * 6.67 * 10^-11 / (10000000)^2 = 2001000 M/S^2 (I love Google Calculator), or roughly 200000G's that each star applies to the other. Total acceleration: 4002000 M/S^2.
And what speed will they have when they collide?
This is kinda tricky, because they don't just start from rest and fly into eachother (which would no doubt be awesome to watch from a distance). But imagine that two neutron stars just pop up 10000km from each other. Each has a gravitational potential relative to the other: mass * integral g(h) dh from 10k to 10m, where g(h) is gravity at height h (2*10^20 / h^2), or the energy to raise one star's mass from the surface of the other to 10 thousand KM. I get 5 * 10^46 joules each. As they fall, potential turns to kinetic energy: 5 * 10 ^ 46 = .5MV^2 = .5 * (3 * 10^30)V^2. V works out to 182 574 186 meters per second. This is a relativistic speed, so things get wierd and I give up. This never happens though - they spiral around each other, losing orbital speed to gravitational waves until their mutual orbit decays into impact.
Finally, what will be the kinetic force at the time of impact?
I don't think our knowledge of motion even applies to something this massive moving this fast, aka I don't have a clue.

Re:You're right, they're massive enough. (1)

Phanatic1a (413374) | more than 8 years ago | (#13728961)

Talk about needlessly complicating issues. Integrals? Yeesh.

Graviational potential energy between two bodies is -G*(m1m2)/r, so that's 6.673E-11 * (3E30*3E30)/10000km, for just about 6E43 joules, so you're a few orders off. Head-on collision between two bodies of equal mass means each contributes half of that energy,
so each one's contributing 3E43 joules. 3E30kg body would have to be moving at 4472135 m/s to do that. That's 1.49% of c, so it's not strongly relativistic, with a gamma of 1.00011113.

Re:You're right, they're massive enough. (1)

The Master Control P (655590) | more than 8 years ago | (#13732089)

-G*(m1m2)/r IS the integral of m1m2G/r^2, except I was thinking that it was integrated from h1 to h2 (10km at the surface to 10000km distance) rather than from h2 to infinity

Re:You're right, they're massive enough. (0)

Anonymous Coward | more than 8 years ago | (#13728857)

The neutron stars will spiral in towards each other, so before impact they will be orbiting each other with a seperation of the two radii (actually tidal forces will have torn them into a torus about the common centre by then).

Orbital speed at that seperation will be a significant proportion of the speed of light (square root of escape velocity of the neutron star, which may approach the speed of light).

Therefore kinetic energy is a significant fraction of the total rest mass of the two stars, i.e. the energy released will be getting on for as much as colliding a star with another one made of anti-matter. That's a big bang!

Re:You're right, they're massive enough. (0)

Anonymous Coward | more than 8 years ago | (#13728918)

square root of escape velocity

That should have been escape velocity / root 2 of course!

Re:You're right, they're massive enough. F!=a. (1)

PoorLenore (608332) | more than 8 years ago | (#13729496)

The greater the mass, the greater the force, not the acceleration. Go and get a cannon ball and a ping-pong ball and drop them from the top of the Leaning Tower of Pisa. (Caveats: blah, blah, air resistance, blah, blah, higher order relativistic effects, blah, blah, apocryphal story, blah, blah...)

Re:You're right, they're massive enough. F!=a. (1)

SimilarityEngine (892055) | more than 8 years ago | (#13729622)

Force of attraction = G * m_1 * m_2 / r^2

Thus, acceleration of first body = G * m_2 / r^2 which is proportional to the mass of the second body. Similarly the acceleration of the second is proportional to the mass of the first. I think this is what the GP meant - heavier stars, more accn.

Re:article is slightly misleading... (-1, Redundant)

Anonymous Coward | more than 8 years ago | (#13727929)

I hope no other sun hits ours until I'm old and nearly dead.

They explode, hence blackholes are a impossibility (1)

LogicallyGenius (916669) | more than 8 years ago | (#13727701)

Before becoming a blackhole any star will explode explode due to fusion of heavy atoms, the heavier they are more energy they will release. like the heavy metals

Re:They explode, hence blackholes are a impossibil (0)

barneyfoo (80862) | more than 8 years ago | (#13727726)

The proof offered for the existence of blackholes doesn't convince me. Just because there is a solution to the GR equations doesn't make it physically real.

Unfortunately these ideas are so institutionalized that there won't be much respect paid to challengers.

Re:They explode, hence blackholes are a impossibil (0)

Anonymous Coward | more than 8 years ago | (#13727828)

Got a better explanation for the evidence?

Re:They explode, hence blackholes are a impossibil (2, Insightful)

Yahweh Doesn't Exist (906833) | more than 8 years ago | (#13727835)

>The proof offered for the existence of blackholes doesn't convince me. Just because there is a solution to the GR equations doesn't make it physically real.

people don't believe they exist just because of a GR solution.

they were predicted before GR but believed to be a mathematical trick that would need perfect conditions to form (perfectly symmetrical mass distribution). GR just changed that by removing these conditions (the generation of gravitational waves by mass distributions with a quadrupolar moment means).

anyway, you make it sound like it's just a case of GR for black holes. it's not - it's a huge amount of theory and observations that are all consistent. if you want respect then the first thing to do is acknowledge this work exists, and the second is to provide an alternative explanation that works at least as well.

Re:They explode, hence blackholes are a impossibil (1)

barneyfoo (80862) | more than 8 years ago | (#13729045)

My statement wasn't clear. I don't mean that GR is the is the only thing supporting black holes.

Your demands are very high. Providing alernative theories/explainations for observational data most physicists don't know exist is quite out of my reach. (after all physics has gone under the same brutal specialization that other fields have)

By the same token, I could criticize your statements as dubiously adherent to an entrenched model that you probably know far less about than you're letting on.

Re:They explode, hence blackholes are a impossibil (1)

arodland (127775) | more than 8 years ago | (#13732658)

By the same token, I could criticize your statements as dubiously adherent to an entrenched model that you probably know far less about than you're letting on.

You could, but you'd still be in the uncomfortable position of finding (if you ever bothered to do your own investigation into the matter) that GP's theories fit very well with our current understanding of the universe, and that you don't have a better alternative. It's a "put up or shut up" kind of deal.

Re:They explode, hence blackholes are a impossibil (2, Interesting)

norton_I (64015) | more than 8 years ago | (#13727895)

There is a lot of experimental evidence for black holes, evidence not well explained by any other known theory. Even after black holes were found to be a possible solution to the GR field equations, people were hesitant to accept them as a "physical" solution. It was only a large body of evidence that has convinced us that they exist.

Despite what you may believe, physicists will listen to challenges to almost any theory (and are proven wrong on a regular basis, science advances!). However, if you just say something can't happen because it is patently silly, without providing a compelling alternative explanation of loads of experemental results, you will be dismissed out of hand. Also, the longer and more successfully a theory has been used, the more substantial evidence against it you will need. Black holes have only been accepted for a short period of time, but if you challenge conservation of energy be prepared. Extraodinary claims require extraodinary evidence.

Also, frequently an outsider to a field will have an alternate theory rejected immediately not because it is absurd but because the experts have already thought of it, done the calculations, and shown that that explanation is inadequate.

Of course, scientists make mistakes, too, but not usually for long in the face of strong evidence.

Astronomy vs Science (1, Informative)

Markus Registrada (642224) | more than 8 years ago | (#13728271)

physicists will listen to challenges to almost any theory (and are proven wrong on a regular basis, science advances!) ... Black holes have only been accepted for a short period of time, but if you challenge conservation of energy be prepared. ... scientists make mistakes, too, but not usually for long in the face of strong evidence.

What this implies is that astrophysics, as practiced, is no more science than, say, sociology. Whenever current astrophysical theories are falsified by observation, a fundamental law gets tossed instead. Lately we have "dark matter" (6x as much of it as the visible universe), "dark energy" (18x as much!), "inflation", and distant galaxies producing hundreds of times more light than similar modern ones. All are futile attempts to rescue the Big Bang from the oblivion it earns by being, finally, irreconcilable with observation. (E.g. light-element ratios; gravitational lensing measurements of galactic mass; fractal, filamentary arrangement of galactic superclusters; preferred direction of cosmic microwave background anisotropy; shall I go on [bizland.com]?)

For all the claims of evidence for the role of neutron stars and black holes in galactic-scale events, it all amounts to negative evidence: those are the only way to concentrate enough energy when the only forces you are willing or equipped to work with are gravitation, fusion, and shock waves. Even so, multimillion-degree "hot gases" in free space and 10^14 eV cosmic rays remain beyond their capacity. Current flow in interstellar plasmas [lanl.gov] easily propagates and concentrates such energies, without reliance on untestable physical laws and ghosts. However, such work can, as a rule, only be published in Plasma Science journals not read (and perhaps not readable) by astrophysicists.

[p.s. read this quick; /. moderators prefer to prevent discussion of failures of mainstream cosmology and astrophysics.]

Re:Astronomy vs Science (3, Insightful)

Anonymous Coward | more than 8 years ago | (#13728749)


What this implies is that astrophysics, as practiced, is no more science than, say, sociology.

You have something against sociology? It's a science too. And ALL sciences are practiced by human beings, who need to be convinced by evidence -- as they should.

Whenever current astrophysical theories are falsified by observation, a fundamental law gets tossed instead.

This, of course, is nonsense. The vast majority of new astrophysical phenomena find explanations within current physics.

y. Whenever current astrophysical theories are falsified by observation, a fundamental law gets tossed instead. Lately we have "dark matter" (6x as much of it as the visible universe), "dark energy" (18x as much!), "inflation", and distant galaxies producing hundreds of times more light than similar modern ones.

And your point is what? There is substantial evidence in favor of these theories, and all competing theories advanced so far have failed. Sometimes new physics is discovered, you know. Just because you want to stick your fingers in your ears and ignore the evidence in its favor, doesn't mean it's not there.

All are futile attempts to rescue the Big Bang from the oblivion it earns by being, finally, irreconcilable with observation. (E.g. light-element ratios; gravitational lensing measurements of galactic mass; fractal, filamentary arrangement of galactic superclusters; preferred direction of cosmic microwave background anisotropy; shall I go on?)

What the hell are you talking about? All of those observations SUPPORT Big Bang cosmology, rather than contradict it. (Except for one mistake on your part: there is no known preferred direction of the CMBR -- but even if there was, there are anisotropic Big Bang cosmologies with preferred directions.)

For all the claims of evidence for the role of neutron stars and black holes in galactic-scale events, it all amounts to negative evidence: those are the only way to concentrate enough energy when the only forces you are willing or equipped to work with are gravitation, fusion, and shock waves.

It is not negative evidence. Theories of neutron stars and black holes make specific predictions of what you will see, and those predictions are supported by observations.


Even so, multimillion-degree "hot gases" in free space and 10^14 eV cosmic rays remain beyond their capacity.

This turns out not to be the case. Ultra high energy cosmic rays, for one, are within the capacity of jets from supermassive black holes. One current goal is to localize the origin of these rays better to see whether they coincide with such sources.

The bigger mystery is not whether mechanisms exist to produce them, but why these rays are appearing to exceed the GZK cutoff, which sets an upper bound on the energy of distant cosmic rays that we can detect. (Some possibilities: the experiments are miscalibrated, which is distinctly possible since HiRES and AGASA's curves look the same except one is shifted by 20%; the cosmic rays are nearer in origin than we think; there is new physics or an unaccounted effect that allows violation of the GZK prediction. All are being investigated, and new expriments such as the Pierre Auger observatory should shed light on this question.)

Current flow in interstellar plasmas easily propagates and concentrates such energies, without reliance on untestable physical laws and ghosts. However, such work can, as a rule, only be published in Plasma Science journals not read (and perhaps not readable) by astrophysicists.

Oh, I get it, you're a plasma cosmology crank. Well, no, you're wrong: plasma physics gets published in astrophysics journals all the time. Just look at the astro-ph arXiv. However, crank physics which purports to explain astrophysical observations with implausible or simply falsified explanations does not get into such journals.

[p.s. read this quick; /. moderators prefer to prevent discussion of failures of mainstream cosmology and astrophysics.]

Hardly. Armchair physicists get modded up all the time by /. mods, who lack the education to detect scientific B.S. such as yours.

Re:They explode, hence blackholes are a impossibil (2, Informative)

barneyfoo (80862) | more than 8 years ago | (#13729127)

Conservation of energy is already violated according to current annihilation theory. When a positron and electron "annihilate" the energy of the outgoing photons does not include the intrinsic angular momentum energy of the electrons. It dissapears, supposedly.

Re:They explode, hence blackholes are a impossibil (1)

DavidTC (10147) | more than 8 years ago | (#13731119)

Oh, that's easy to explain.

It doens't disappear, it just pushes the universe. ;)

Re:They explode, hence blackholes are a impossibil (1, Informative)

Anonymous Coward | more than 8 years ago | (#13731540)

This is not correct. Both total energy and total angular momentum are conserved in particle-antiparticle annihilation.

Re:They explode, hence blackholes are a impossibil (1)

kmac06 (608921) | more than 8 years ago | (#13733060)

I think the anon poster above me is right. Do you have a link stating this?

Re:They explode, hence blackholes are a impossibil (2, Informative)

barath_s (609997) | more than 8 years ago | (#13727991)

It's not just because there is a solution ... there are cases where the observations are such that no other solution per the proven theory seems plausible

http://www.wonderquest.com/black-holes-proof.htm [wonderquest.com]
Summarizes very neatly the default hypothesis that they exist

This leaves aside the problem of coming up with a better theory than GR (which has been extensively tested)

After all, the theory of black holes has been contested vigorously from its inception http://en.wikipedia.org/wiki/Chandrasekhar_limit [wikipedia.org]
http://www.newscientist.com/article.ns?id=dn6193 [newscientist.com]

Two examples of a reasonable approximation to proof:
Massive black holes ... Here they seem to have shown that MACHOs and WIMPs do not fit the bill.
http://www.space.com/scienceastronomy/blackhole_mi lkyway_021016.html [space.com]

And for a stellar mass black hole
http://www.space.com/scienceastronomy/astronomy/de ath_spiral_010111.html [space.com]

Re:They explode, hence blackholes are a impossibil (1)

Decaff (42676) | more than 8 years ago | (#13728204)

there are cases where the observations are such that no other solution per the proven theory seems plausible

There are alternatives, for example the gravastar:

http://www.absoluteastronomy.com/encyclopedia/g/gr /gravastar.htm [absoluteastronomy.com]

Such alternatives would yield the same observations.

There are major problems with current black hole theory - for example, the information paradox, and the central singularity. I think it is pretty reasonable to state that current black hole theory is at the very least incomplete, if not actually wrong.

Re:They explode, hence blackholes are a impossibil (1)

DavidTC (10147) | more than 8 years ago | (#13731290)

Erm, the problem with gravstars is we know there is no 'quantum gravity' theory even slightly likely to appear in a reasonable amount of time.

Or did you miss the recent discovery that gravity does not exhibit quantum effects? It was actually posted on here a few months ago.

That's not to say we will never have a quantum gravity theory, but simple 'gravitons' seem unlikely. Gravity just does not work like the electronuclear forces.

A lot of people have built a quantum gravity house of cards, but those people seem likely to be disappointed.

And the information paradox has, as far I know, has been solved by Hawking's discovery that black holes can 'emit' energy.

Re:They explode, hence blackholes are a impossibil (1)

Decaff (42676) | more than 8 years ago | (#13731777)

Erm, the problem with gravstars is we know there is no 'quantum gravity' theory even slightly likely to appear in a reasonable amount of time.

That is like saying that electrons can't exist because we don't understand what they are! Just because we don't have a theory of quantum gravity does not mean that gravity does not exhibit quantum effects.

Or did you miss the recent discovery that gravity does not exhibit quantum effects? It was actually posted on here a few months ago.

I did. URL?

That's not to say we will never have a quantum gravity theory, but simple 'gravitons' seem unlikely. Gravity just does not work like the electronuclear forces.

This statement is directly contradicted by the most popular approaches to unification - loop quantum gravity and string theory. String theory states explicitly that there are simple gravitons and they do work like the electromagnetic, strong and weak forces - they are simply different string vibration modes.

And the information paradox has, as far I know, has been solved by Hawking's discovery that black holes can 'emit' energy.

That is not even published, and many are doubtful. Hawking has been wildly wrong many times before.

Re:They explode, hence blackholes are a impossibil (1)

Decaff (42676) | more than 8 years ago | (#13733423)

And the information paradox has, as far I know, has been solved by Hawking's discovery that black holes can 'emit' energy.

Sorry for previous comment - I assumed you meant Hawking's recent conjecture that black holes can emit information.

The emission of energy does not help the information problem, as the energy emitted bears no relationship to the material that made up the black hole.

Re:They explode, hence blackholes are a impossibil (4, Informative)

The Master Control P (655590) | more than 8 years ago | (#13727897)

What are you talking about? Fusion only produces energy in elements lighter than Iron, and fission only produces energy in elements heavier than Iron. Iron is the most tightly-bound nucleus (most eV / nucleon) - If you fuse it with another nucleus, the nuclear binding energy of the result will be higher than what you started with, and you lost energy. Furthermore, the energy yield from fusion is highest with hydrogen & helim and decreases rapidly as masses increase.

If you'd like to learn more, type "nuclear binding energy" into Google.

Re:They explode, hence blackholes are a impossibil (1, Informative)

Anonymous Coward | more than 8 years ago | (#13728853)

Fission splits up big atoms into smaller (lower atomic number) ones, so you can't get heavy elements from fission. Fusion is the only process that creates heavy elements. True, fusion to create elements heavier than iron loses energy, but that's why stars die after they start such reactions.

Re:They explode, hence blackholes are a impossibil (1)

kmac06 (608921) | more than 8 years ago | (#13732992)

Stars don't ever really start such reactions in the first place. I believe there can be trace amounts of nuclei heavier than iron produced in a star, but almost all heavier nuclei are created in a supernova, when atoms are hit with a ton of neutrons. So production of the heavy elements (ie supernova) has little to do with the burning that goes on prior to it.

Re:They explode, hence blackholes are a impossibil (0)

Anonymous Coward | more than 8 years ago | (#13727919)

Looks like someone hasn't done his research.

Fusing elements heavier than iron require more energy than they release. Didn't you wonder why we've been trying to fuse light elements like hydrogen and helium, and not plutonium?

Re:They explode, hence blackholes are a impossibil (2, Informative)

Decaff (42676) | more than 8 years ago | (#13728131)

Before becoming a blackhole any star will explode explode due to fusion of heavy atoms, the heavier they are more energy they will release. like the heavy metals

This is false. Fusion of atoms only releases energy if the atoms are light. Above a certain nuclear size (greater than Iron) fusion takes energy.

Re:They explode, hence blackholes are a impossibil (5, Informative)

Floody (153869) | more than 8 years ago | (#13728196)

Before becoming a blackhole any star will explode explode due to fusion of heavy atoms, the heavier they are more energy they will release. like the heavy metals


That isn't really the primary (theoretical, of course) reason that massive stars "explode" (keep in mind, this is nothing like an explosion as any human understands it). However, the continuing fusion of heavier elements, up to iron, is thought to be the reason for numerous changes a late-lifecycle star experiences.

Once a massive star reaches the point where the majority of exothermic fusionable material consists of silicon, it has very big problem on its "hands." It's got about a day to live. silicon fuses at about 2.7e+9 K (optimimally), so that's one hell of a last day, and an unbelievable amount of iron production (thank the stars for your iron). Now, this entire time the star has been increasingly putting out more and more energy; that energy has tremendous pressure and serves to balance the star's own gravitional force which seeks to collapse it as closely to a point-source as possible (and it is, of course, theorized ... sometimes it gets its wish).

At some very critical moment on the last minute of the last hour of that last day, there is no longer enough remaining silicon to keep the reaction going (some of the iron is fusing, but it's endothermic so it's only making the situation worse). Once this magic point is hit, fusion drops off very very rapidly, the remaining lighter-than-iron elements simply won't fuse without enough energy and once its gone ... its gone forever (for that star anyway). Suddenly, gravity has the upper-hand, and in a big way. The entire star begins to contract in on itself, approaching relativistic speeds as it nears the core. The inner core of the star is already highly dense post-fusion material, lots of iron, silicon, oxygen, neon, etc. The outer portion of the star was mostly the light and fluffy stuff: hydrogen, helium, nitrogen, ... But there's a whole lot of it. So, when all this "stuff" comes rushing back in and hits what amounts to an immovable object, it "bounces." Really really hard. So hard that the fundamental forces of nature momentarily cease to exist as we know them. So hard that the energy produced illuminates large sections of galaxies.

The details that actually occur in those few nanoseconds and microseconds are not completely understood, but it is understood that a great many bizarre interactions take place. The closest anyone can come to understanding this by way of simulation is in a particle accelerator. For one brief moment, this former mega-sized celebrity of a star takes on the apparition of the big bang; unification of forces and other outlandish stylings that no mortal human will ever witness up-close (or would want to if you're half-sane).

So, what really causes supernovae? Gravity winning.

Re:They explode, hence blackholes are a impossibil (1)

kmac06 (608921) | more than 8 years ago | (#13733040)

According to the notes I took in Astrophysics a couple days, ago, when the core collapses, it goes from R ~ 7000km -> R = 50km in under a second. Pretty quick contraction...

I never thought I'd use physics notes for a post on /....

Correction... (2, Interesting)

Adi42 (920652) | more than 8 years ago | (#13727709)

It's actually about colliding neutron stars...

Anyway, it is curious that no gamma-ray bursts occured in our galaxy (yet). It is supposed that such an even would generate enough gamma rays to wipe out the ozone layer, and cause life extinction on earth.

Wait... why dinosaurs dissapeared again? :-)

Re:Correction... (2, Funny)

fido_dogstoyevsky (905893) | more than 8 years ago | (#13727761)

Anyway, it is curious that no gamma-ray bursts occured in our galaxy (yet). It is supposed that such an even would generate enough gamma rays to wipe out the ozone layer, and cause life extinction on earth.

Wait... why dinosaurs dissapeared again? :-)


I thought it was because they took up smoking...

Re:Correction... (1)

ThinkOfaNumber (836424) | more than 8 years ago | (#13727841)

> > Wait... why dinosaurs dissapeared again? :-)
> I thought it was because they took up smoking...

No, no! It's because Homer sneezed when his modifed toaster took him back in time, remember?

Re:Correction... (1)

layer3switch (783864) | more than 8 years ago | (#13727906)

Correct me if I'm wrong, but didn't dinosaurs extinct over a period of time, long enough to evolve and adapt to changing environment?

And not only that, extinction in mass scale doesn't seem to "sanitize", but "life" seems to find its way out of harsh environment or adapt. Matter of fact, didn't theropod dinosaur survive? After all, what are all these birds doing on earth?

Re:Correction... (1)

Decaff (42676) | more than 8 years ago | (#13728140)

Correct me if I'm wrong, but didn't dinosaurs extinct over a period of time, long enough to evolve and adapt to changing environment?

No. Many species of dinosaur became extinct of a period, but at a slow rate. The latest evidence is that the final extinction which wiped out the rest was very fast indeed.

And not only that, extinction in mass scale doesn't seem to "sanitize", but "life" seems to find its way out of harsh environment or adapt. Matter of fact, didn't theropod dinosaur survive? After all, what are all these birds doing on earth?

The exact relationship between birds and dinosaurs is controversial. What did seem to happen is that some extinction event (most likely an asteroid collision) wiped out most large species. Things that could burrow or hide from the heat survived, which would have included birds.

Re:Correction... (2, Informative)

Decaff (42676) | more than 8 years ago | (#13728151)

Anyway, it is curious that no gamma-ray bursts occured in our galaxy (yet).

They may have, but not pointed in our direction.

It is supposed that such an even would generate enough gamma rays to wipe out the ozone layer, and cause life extinction on earth.

Wiping out the ozone layer would not cause extinction of life, after all, life survived for billions of years without such a layer.

Re:Correction... (1)

Ihlosi (895663) | more than 8 years ago | (#13728166)

It is supposed that such an even would generate enough gamma rays to wipe out the ozone layer, and cause life extinction on earth.



If the burst occurs close enough (a few lighyears, maybe even a few tens of lightyears should do), it would essentially sterilize the side of the planet that is facing towards the source of the burst.



Death Stars are for tourists.

Re:Correction... (1)

tabbser (560130) | more than 8 years ago | (#13728226)

Did you read the article at all ?

This gamma ray burst was from within our galaxy !

A GRB of this size within 10 light years would be enough to disrupt (read species die out) on earth.
The nearest worrying sources, magnetars, around 4000-5000 light years away.

Please, please, please, do a little google searching before opening your mouth.

Re:Correction... (1)

stevelinton (4044) | more than 8 years ago | (#13728430)

No. The two GRB's they are interested in were about 1 billion light years away -- well outside our galaxy, but closer than the regaular long-duration GRBs which are several billion lys away.

You may be confusing this with the recent outburst from (probably) a magnetar on the other side of the galaxy, which is a Soft Gamma Repeater (SGR), a different thing again.

Re:Correction... (1)

mark_osmd (812581) | more than 8 years ago | (#13729744)

the article specifically says: "Astronomers now know the event took place on the outskirts of a faraway galaxy, a location where old stellar remnants like neutron stars are known to reside." 'Faraway galaxy' doesn't sound like it was our galaxy

Re:Correction... (1)

jellomizer (103300) | more than 8 years ago | (#13728536)

So with a Gamma-ray burst it caused all the Mammals into huge green invincible creatures that killed all the dinosaurs when they got angry.... Cool.

TRex to Big mouse thinggy. I am going to eat you.
Mouse: I am getting angrrrrrrryyy. Rarrrr! Mouse Smash!!
THen the mouse beats up the TRex

p00p (-1, Offtopic)

Anonymous Coward | more than 8 years ago | (#13727738)

reeeeeee

As Einstein once said... (-1, Offtopic)

Anonymous Coward | more than 8 years ago | (#13727748)

"Imagination is more important than knowledge."

Gravity Waves (4, Informative)

williwilli (639147) | more than 8 years ago | (#13727758)

The end part of the article notes that the upcoming LIGO observatory might see the first detection of gravitational waves, corresponding with a GRB event! Evidentially Einstein modeled the emission of gravity waves during a collision between Neutron stars. This is interesting because we don't really know much about gravity; e.g. if it is a wave or a constant. More info on LIGO is available here. [caltech.edu]

free music, games, recipes, and more! [earth2willi.com]

Re:Gravity Waves (2, Informative)

Decaff (42676) | more than 8 years ago | (#13728229)

This is interesting because we don't really know much about gravity; e.g. if it is a wave or a constant.

We are pretty sure it is a wave because we have seen the effects of gravitational radiation (of waves) in double neutron star orbits. If gravity isn't waves, then general relativity is in trouble, which is unlikely.

Re:Gravity Waves (3, Informative)

PhilRod (550010) | more than 8 years ago | (#13728478)

The paper itself suggests that observing the waves from such an event would have to wait until the "second generation" LIGOs. I assume by that it means advanced LIGO [caltech.edu], which isn't scheduled to start taking measurements until 2013, so don't hold your breath :-). Even so, LIGO is an amazing project - the sensitivities required are enormous, (to quote the LIGO website: "These changes are minute: just 10-16 centimeters, or one-hundred-millionth the diameter of a hydrogen atom over the 4 kilometer length of the arm"), and the payoffs for theory and astronomy are potentially huge.

As to whether gravity is a wave, that's generally agreed (as someone else pointed out, measurements of binary pulsars show this). However, the exact details of general relativity in the strong field regime - that is, near black holes, neutron stars, etc - hasn't been well tested, and there are potentially modifications of general relativity which would give the same predictions for the weak field case (eg, the solar system), but would differ for strong fields. Physics World has a nice article on it [physicsweb.org].

Re:Gravity Waves (1)

drauh (524358) | more than 8 years ago | (#13730023)

LIGO is not just "upcoming". It's already running, though not 24x7x365, and taking data. You can see some of the early papers at the preprint archive [arxiv.org]: search for "LIGO" in the author field.

i liek pr0n (-1, Offtopic)

Anonymous Coward | more than 8 years ago | (#13727772)

please keep all posts on topic or cowboyneal will sit on you

The animation NASA had was cool... (1)

ockegheim (808089) | more than 8 years ago | (#13727838)

Would the explosion at the end have be when the majority of the neutron star mass hits the black hole's event horizon?

Re:The animation NASA had was cool... (1, Informative)

Anonymous Coward | more than 8 years ago | (#13728578)

No. In fact, nothing would be seen: the horizon is not a physical surface that a star can "smack into", but a region of space within which light can't escape. In fact, that is one of the main new ways we have found to justify the existence of black holes: when things run into them and you don't see a big flash from a collision.

Science Meets Film Noir (4, Funny)

MooseByte (751829) | more than 8 years ago | (#13727941)


"Our observations do not prove the coalescence model, but we surely have found a lady with a smoking gun next to a dead body," said Shri Kulkarni

Looks like the Sin City [imdb.com] DVD has been getting a lot of play time down in the lab....

Re:Science Meets Film Noir (0)

just_another_sean (919159) | more than 8 years ago | (#13729042)

Yeah, what I want to know is why it has to be women with a smoking gun? I mean, if a man is caught with a smoking gun over a body he's "taking control of the situation", but if it's a women everyone immediately suspects the worst. Sheesh, when are we gonna get some equality people?

you don't say... (1)

paran0rmal (799476) | more than 8 years ago | (#13727973)

Collisions of the cosmic kind could be the source of one of nature's most lethal explosions

Amazing! And here I thought collisions of the microscopic kind caused the most lethal explosions...

A few questions about GRBs (2, Interesting)

MAdMaxOr (834679) | more than 8 years ago | (#13727981)

What is the typical frequency? (i.e. 1x per galaxy per 100k years)
What is a typical duration?
How close would you have to be to one to receive a lethal radiation dose?

Re:A few questions about GRBs (2)

tabbser (560130) | more than 8 years ago | (#13728236)

a) Not many, SWIFT detects between 30 and 300 a year, only a handful a year from our galaxy (I think)
b) From less than a second, to a few seconds. VERY brief.
c) A decent magentar flare or decent neutron merger within 10 light years would be enough to disrupt life (read species would die out)

The nearest magnetars are 4000-5000 light years away.

It does beg the question thoughL Which poor people got burned on this burst ?

Re:A few questions about GRBs (2, Insightful)

imsabbel (611519) | more than 8 years ago | (#13729507)

If there were "a few per year" from our galaxy, live would have never evolved on earth... (just think about it: a few per year over the the time earth exists is about 10 billion GRBs ....

I dont know if we _EVER_ have observed a GRB in our galaxy, the detected ones are very isotropically distributed over the sky and in the _deep_ background. Most have a z>0.1 and are FAR away.

And the killing ratio for a GRB would be more like 100-250 ly. 10 ly away even a normal supernova would be an extinction event.

Just use some fermi logic:
If a GRB is the result of the collision of 2 neutron start, than they are at least twice as rare as supernovas (somewhere those NS have to come from, plus many supernovas dont leave a neutron star).
and after that, there has to be a situation when 2 are able to merge (which 99.9% only happens in close binary start, as 2 neutron start hitting each other has a laughably small propability).

This alone allows to fix the rate of GRBs to at least as rare as once per millenium.

Re:A few questions about GRBs (3, Informative)

hde226868 (906048) | more than 8 years ago | (#13729711)

I do research in X-ray and Gamma-Ray astronomy and just wanted to confirm that so far no gamma-ray bursts have ever been observed to come from our own galaxy.

The summary (2, Interesting)

barath_s (609997) | more than 8 years ago | (#13728150)

I liked the FAQ :
http://www.astro.caltech.edu/~ejb/faq.html [caltech.edu]

especially the portion that said ...." In practice, over the few seconds that a gamma ray burst occurs, it releases almost the same amount of energy as the entire Universe! " The article posted on Slashdot is on the short and hard type

Re:The summary (3, Insightful)

Decaff (42676) | more than 8 years ago | (#13728243)

especially the portion that said ...." In practice, over the few seconds that a gamma ray burst occurs, it releases almost the same amount of energy as the entire Universe! "

Which is, of course, nonsense. It should say 'the same amount of energy as the visible Universe'. Big (very, very big) difference!

A brief history of time (2, Funny)

marvy666 (215740) | more than 8 years ago | (#13728172)

Just been reading a brief history of time, 10th anniversary edition today. And i could swear this is spoken about in the book.

Then again I could be wrong, a lot of it is over my head.

Re:A brief history of time (1)

meringuoid (568297) | more than 8 years ago | (#13730819)

Just been reading a brief history of time, 10th anniversary edition today. And i could swear this is spoken about in the book.

It is. Gamma-ray bursts have been observed for a long time: they were first discovered by spysats designed to watch out for nuclear test ban violations. ISTR that it was initially thought that the Soviets were trying to evade the ban by testing in deep space, but it soon became clear that these explosions were from much further afield.

The collision of neutron stars has always been the most popular candidate for the source of these blasts: neutron stars are an already well-known feature of the universe, and given their enormous gravity, a collision between two of them would certainly be sufficiently energetic. However, there has never been any direct evidence that they are the cause - until now, apparently.

You should be ashamed...! (0)

Anonymous Coward | more than 8 years ago | (#13728284)

"A *LADY* with a smoking gun..."? Why a lady? You're saying that only women are killers? That's sexist and you're a pig!

So... Colliding stars, eh? (1)

hey! (33014) | more than 8 years ago | (#13728518)

How long do you think before God posts the MPEGs on his web site?

Actually I have a pretty good idea of what's on his site looks like. They'll be somewhere between pages about playing with metallic sodium and his beer recipes.

I don't know about you (1)

ValuJet (587148) | more than 8 years ago | (#13729797)

Astronomers have traced the origin of short-duration gamma-ray bursts But I'd be pretty warry about making anyone from that region of space angry.
Load More Comments
Slashdot Account

Need an Account?

Forgot your password?

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>
Sign up for Slashdot Newsletters
Create a Slashdot Account

Loading...