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Published online 21 March 2008 | Nature | doi:10.1038/news.2008.687
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Powerful stellar blast sighted
Light from cosmic explosion traversed half the universe.
Scientists have discovered a record gamma-ray burst, a massive explosion that occurred halfway across the universe but was so bright that its optical flash was briefly visible to the naked eye.
Gamma-ray bursts are high-energy explosions seen as shockwaves jet out from a massive dying star.
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So, is the energy detected from this event actually 7.5 billion years old? Doesn't that affect the photons wavelength too? Was there an actual "visible" spectrum detected also? Thank you Jim
Hi Jim, Yes, the explosion took place 7.5 billion years ago, the photons have only just reached us. Are the photon's wavelength affected? Yes, the cosmological redshift almost doubled the wavelengths by the time they reached us. (The emitting surface was travelling towards us at a very high fraction of the speed of light however, this causes the pre-cosmologically-redshited photons to have a very much shorter wavelength than they would have in the inertial frame of the emitting surface.) I am not quite sure what you meant in your last question. There was no prompt dispersed spectrum obtained unfortunately, although the redshift (and thus distance) was determined from a dispersed spectrum of the afterglow about an hour after the burst. If you mean 'were photons emitted in the visible detected?', then the answer is probably, as the REM Italian IR telescope in Chile pointed at the burst within 43 sec and it was still very bright at that time. Julian Osborne - www.swift.ac.uk
I venture to say that the magnitude of this event is beyond comprehension of any human being, so is the time scale. As to the significance, who knows what effect now has an event that took place 7.5 billion years ago? To me this news item (i.e., here today, gone tomorrow) raises not any practical but rather philosophical questions of our insignificance in the overall scheme of things. No one can and should even try to limit anyone in the 'flight of fancy', that is where 'advances' come from. But I have this nagging feeling that we should first of all strive to solve and advance things we do, or should understand, "down here", on this tiny speck of dust of the Universe...
What is the highest frequency--shortest wavelength--gamma ray known, or possible? If this frequency happens to be exceeded, as for example if the wave front of the expanding explosion is approaching us at a high ratio to the speed of light, would these extremely energetic gamma rays disappear into positrons and electrons or other mass particles? And therefore, might not there be extreme explosions that are not visible to us?
Karel Petrak is exactly right, "we should first of all strive to solve and advance things we do, or should understand, "down here", on this tiny speck of dust of the Universe." If those working on NASA’s Swift satellite would first take the time to study the rest masses of the 3,000 different types of stable and radioactive nuclei that comprise all the material in the solar system (shown below in the "Cradle of the Nuclides"), they might have a chance to understand the significance of powerful stellar explosions like this one. http://www.omatumr.com/Data/2000Data.htm Otherwise NASA’s Swift satellite will be a waste of public funds on the adult version of the child's game, "Guess what I saw!" Neil Gehrels, Peter Mészáros, and others working on data from NASA's Swift satellite are encouraged to respond.
I'm not sure K.P. meant what O.M. ascribed, but the latter comments are certainly mistaken. We shall never understand atomic nuclei unless we do cosmology and astrophysics; or viceversa. After all, the former come from the Big Bang and stellar nucleosynthesis. The detection and interpretation of gamma-ray bursts is one of humanity's outstanding achievements. A prior event, 050904, occurred at a lookback time of 13 Gyr. If our best minds had been asked a decade or so earlier, shall we ever be able to observe an event in the life of a single star at that epoch (0.7 Gyr after the Big Bang), most would likely have answered, never (well, maybe not, but I would have!); but now we have, thanks to the intellectual and technical virtuosity of some of them. The scientific and philosophical implications of this accomplishment are enormous.
Nolan indiscriminately confuses his opinions and scientific models with scientific data. He claims that "We shall never understand atomic nuclei unless we do cosmology and astrophysics; or vice versa." In fact, we shall never understand atomic nuclei unless we pay attention to the experimental data on atomic nuclei. Nolan states that atomic nuclei "come from the Big Bang and stellar nucleosynthesis." That is his opinion. It may or may not turn out to be correct. I know several good astronomers who doubt that there was a Big Bang. So do I. Nolan says that the "detection and interpretation of gamma-ray bursts is one of humanity's outstanding achievements." I have a rather different opinion of the interpretation of stellar explosions by scientists who do not understand the implications of the 2,850 data points that represent all known stable and radioactive forms of atomic matter in the universe http://www.omatumr.com/Data/2000Data.htm Furthermore, Nolan's high opinion of the "intellectual and technical virtuosity" of such scientists is . . . his opinion. - Oliver K. Manuel
I urge anyone who is interested in the nuclear forces that drive stellar explosions to read the paper that Hilton Ratcliffe, Michael Mozina and I submitted to the Hirschegg Workshop on Astro- physics & Nuclear Structure, Hirschegg, Austria, 15-21 Jan 2006 http://arxiv.org/abs/astro-ph/0511379
Oliver, I visited the link you posted, skimmed your note on "The Nuclear Cycle that Powers the Stars...". I'm very much a non-expert, have a couple non-expert questions: 1. You mention a repulsive force between neutrons, but in your paper (which quite honestly I did not read closely) I saw no discussion of the nature of this force. Is what you mention some variant of the commonly accepeted strong nuclear force? Or are you suggesting that there is some 'fifth force' that has not yet been recognized? Or is it just Pauli exclusion? Please, would you clarify this? 2. Regarding your figure 3, the "Cradle of Nuclides", and thinking back to high school physics, I seem to remember a similar cradle that resulted from coulomb repulsion between the protons. see for instance http://en.wikipedia.org/wiki/Image:Binding_energy_curve_-_common_isotopes.svg Your figure 3 appears to be some sort of inverse of the binding-energy-per-nucleon curve. Could/would you elaborate on this a bit, explain how these two are related? Thanks, Peter Cameron
Hi Peter, Thank you for your comments. Answers to some questions are in overheads http://www.omatumr.com/Overheads/Overheads.htm especially overhead #8: http://www.omatumr.com/Overheads/8a.pdf Other answers: 1. Like the repulsive force between negative (or positive) charges, the repulsive force between neutrons is empirical, not theoretical. 2. There is an equal repulsive force between protons, in addition to the repulsive Coulomb force between the + charges on each proton. 3. Like the attractive force between + and - charges, the attractive force between neutrons and protons is empirical. 4. The empirical evidence for answers number 1-3 (above) is illustrated in the "Cradle of the Nuclides." http://www.omatumr.com/Data/2000Data.htm 5. Assigning a name to a force (Coulomb, Pauli, Yukawa, Gravity, Strong, Weak, etc.) does not mean we understand its "nature." 6. The nuclear "Binding Energy" curve that you cite has only about 200 data points. Further, there is an inherent error in the definition of nuclear "Binding Energy" that causes unstable nuclei, like H-3, to have greater "Binding Energy" than its stable decay product, He-3. 7. The nuclear packing fraction (f) defined by Nobel Laureate Francis W. Aston does not have this error. 8. The "Cradle of the Nuclides" shows 3,000 mass data points that represent all radioactive and stable nuclei in the visible universe. 9. The "Cradle of the Nuclides" shows values of M/A (mass or total energy per nucleon) on the vertical scale. Values of M/A = f + 1, where f = the nuclear packing fraction defined by Nobel Laureate Francis W. Aston. Finally, 10. The "Cradle of the Nuclides" shows values of Z/A (nuclear charge density) on each nucleus, where Z = atomic number and A = mass number. So far as I know, values of Z/A (nuclear charge density) are not discussed in any textbooks of physics. [Are you by chance related to a well-known astrophysicist, the late Professor A. G. W. Cameron of Harvard University?]
Quote: [“We at first thought something was wrong with the satellite,†says Swift principal investigator Neil Gehrels, of the Goddard Space Flight Center in Greenbelt, Maryland. “Then we realized it was the most remarkable burst we’ve ever seen.â€] The universe will be mysterious for so long as solar, nuclear, particle and astro- physicists maintain their fixation on the lightest stable nuclear species, H-1, and ignore all of the other 3,000 nuclear data points in the "Cradle of the Nuclides." Information in the "Cradle of the Nuclides" the will quickly destroy their illusion that a.) An imaginary Big Bang created the universe and filled it with the lightest isotope of hydrogen (H-1), that b.) Hydrogen clouds collapsed to form stars, and that c.) Stars are heated by hydrogen fusion. - Oliver K. Manuel