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Short Gamma-ray Bursts Traced to Colliding Stars
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."
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.
$fortune
Tomorrow has been canceled due to lack of interest.
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.
Take off every sig. For great justice.
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?
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.
Quid festinatio swallonis est aetherfuga inonusti?
Africus aut Europaeus?
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.
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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, 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?
>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.
The merger of two dense bodies causes gamma-ray bursts?
Wow! Now I can get rich selling lead underwear the next time there's a Microsoft/AOL merger hoax
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.
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.
"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 DVD has been getting a lot of play time down in the lab....
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?
http://www.wonderquest.com/black-holes-proof.htm
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
http://www.newscientist.com/article.ns?id=dn6193
Two examples of a reasonable approximation to proof: ... Here they seem to have shown that MACHOs and WIMPs do not fit the bill. i lkyway_021016.html
Massive black holes
http://www.space.com/scienceastronomy/blackhole_m
And for a stellar mass black holee ath_spiral_010111.html
http://www.space.com/scienceastronomy/astronomy/d
Neutron stars and other things like them do wierd things: Objects that dense and massive, spiraling around each other that fast, create gravitational waves 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.
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.
;)
The Online Slang Dictionary
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.
http://www.astro.caltech.edu/~ejb/faq.html
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
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.
...with the Electric Universe theory?
Be careful. People in masks cannot be trusted.
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
... sometimes it gets its wish).
... 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.
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
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
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.
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.
This, of course, is nonsense. The vast majority of new astrophysical phenomena find explanations within current physics.
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.
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.)
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.
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.)
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 expl
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.