# Tag Info

## Hot answers tagged supernova

77

It's an incredibly misleading statement, so it's not you. Gravitational waves propagate at the speed of light, so their detection by Earth-bound detectors is expected to correlate with the arrival of light from distant events assuming the source of light generation is identical (not spatially or temporally separated) to the source of the gravitational ...

72

Heavy elements couldn't form right after the Big Bang because there aren't any stable nuclei with 5 or 8 nucleons. Source: Wikipedia (user Pamputt) In the Big Bang nucleosynthesis, the main product was $^4He$, because it is the most stable light isotope: 20 minutes after the Big Bang, helium-4 represented about 25% of the mass of the Universe, and the ...

51

The situation with supernova is not about speed of flight but about time of emergence. A type IIa supernova candidate is big, even with the vastly powerful explosion of the core it takes hours to blow the envelope off and expose the violence of the interior—and it is only after that happens that the star becomes brighter in the electromagnetic spectrum. But ...

39

You can't quite look back in time, unless you can outrun a photon. If you think about it, the event being observed is marked by a release of photons forming a sphere like shape. Once you are inside the sphere, you can observe the event. However, once you are inside, the only way to get outside is to go faster than the wave-front of photons. Unless you ...

39

The micro black hole would be unable to accrete very quickly at all due to intense radiation pressure. The intense Hawking radiation would have an luminosity of $3.6 \times 10^{14}$ W, and a roughly isotropic flux at the event horizon of $\sim 10^{48}$ W m$^{-2}$. The Eddington limit for such an object is only $6 \times 10^{9}$ W. In other words, at this ...

39

The solar abundance of iron is a little bit more than a thousandth by mass. If we assume that all the baryonic mass in the disc of the Galaxy (a few $10^{10}$ solar masses) is polluted in the same way, then more than 10 million solar masses of iron must have been produced and distributed by stars. A type Ia supernova results in something like 0.5-1 solar ...

38

Consider a star of mass $M$ and radius $R$ at a distance $r$ from the supernova. For a back-of-the-envelope estimate, consider how much momentum would be transferred to the star by the supernova. From that, we can estimate the star's change in velocity and decide whether or not it would be significant. First, for extra fun, here's a review of how a typical ...

37

We think that most neutron stars are produced in the cores of massive stars and result from the collapse of a core that is already at a mass of $\sim 1.1-1.2 M_{\odot}$ and so as a result there is a minimum observed mass for neutron stars of about $1.2M_{\odot}$ (see for example Ozel et al. 2012). Update - the smallest, precisely measured mass for a neutron ...

35

In the case of a supernova explosion it is possible to create heavy elements through fusion. Supernovae have a tremendous amount of energy in a very small volume but not as much energy per volume as there was in our early universe. So, what is the major difference? Why didn't the Big Bang create heavy elements? I just want to point out, too much ...

30

A back of the envelope calculation (and that is all this is) would go along the lines of assuming that the white dwarf is made entirely of $^{12}$C (it isn't) and is entirely converted into $^{56}$Ni (it isn't). The appropriate mass to use would be $\sim 1.4M_{\odot}$ (it is actually a touch lower - the real "Chandrasekhar mass" at which instability sets ...

23

Probably not. Supernovae are powerful, but space is really big. ;) Supernova energies are often measured in foe; one foe is $10^{44}$ joules. According to Wikipedia, a big supernova can release around 100 foe as kinetic energy of ejecta, plus 1 to 5 foe for the light & other EM energy released. (The energy of the released neutrinos is higher than the ...

21

I worked this out a little while back in order to check something said on one of these Nova or other science show specials. I wanted to know how much energy would be required to remove the entire atmosphere of the Earth and whether a supernova (or other astronomical event) could possibly do this. Earth's Atmosphere Let's assume the following quantities: $... 20 This question is answered in detail by the so-called "Big Bang Nucleosynthesis", the theory about the creation of the nuclei in the early Universe. Almost out of nothing, it allows one to determine that 75% of the nuclear mass was coming in hydrogen, 25% in helium, and some small traces of lithium appeared, too. Even though Gamow used to think that all ... 18 You're not going to see the explosion twice, that's pretty much against the rules of SR and reference frames. However, with a lot of fortune, we can actually see the light from the remnant a second time (maybe more). Sorta There are things called light echoes, which is an analog to the common acoustic echoes that we are all familiar with. When this occurs, ... 18 There are many misconceptions in your question. First: Most supernovae probably end up as neutron stars, not black holes. Second: The nearest black hole is not CygnusX-1. It maybe the closest one we know about, but a simple calculation reveals that the nearest black hole is likely to be within 20pc and the nearest neutron star at about 10pc. https://... 18 Don Clayton investigated the production of Fe-60 in his 1971 Nature paper New Prospect for Gamma-Ray-Line Astronomy (paywalled, but the abstract also hints to Arnett & Clayton 1970, also paywalled, but that abstract is unclear as to the contents being about Fe-60). This likely would have used supernova nucleosynthesis calculations (see, for example, ... 17 Lithium and other light elements (e.g. beryllium) can be formed indirectly from supernovae via cosmic ray spallation, a process where protons and neutrons are ejected when a cosmic ray collides with another atom. The nuclei can then become new elements. Nakamura & Shigeyama (2004) were able to calculate yields for 6Li, 7Li, and isotopes of Beryllium and ... 17 Peter A. Schneider already gave the correct answer in the comments. Do gravitational waves travel faster than light? No, gravitational waves also travel at the speed of light in vacuum. However, the interstellar medium is not perfectly empty but filled with plasmas which slow electromagnetic waves (light, radio) down by a factor n, the refractive index. ... 16 As always, it depends on what you mean by know/find. As aptly illustrated by Kyle Kanos, theoretical arguments show that$^{60}\mathrm{Fe}$is naturally produced through stellar nucleosynthesis in the last stages of the life of massive stars, and then injected into the InterStellar Medium (ISM) by SN explosions. This has been known, from a purely theoretical ... 15 One supernova has been observed 4 times, over the course of 20 years! This didn't involve the Earth's orbit. Instead, the supernova's light took 4 different routes from its source to Earth, the routes bending due to the gravity of galaxy clusters between the supernova and Earth. Because the lengths of these paths varied by up to 20 lightyears, the light ... 15 General relativity does not have much to do with this. The special theory of relativity does not say that light moves at speed$c$unconditionally; that would contradict experiment: it says that light moves at speed$c$in vacuum. In glass and water, light moves slower because it interacts with matter. While the light was coming from the supernova, of ... 13 No. Ordinary supernovas do not produce neutrinos of large enough energy to cause such a nuclear weapon meltdown, even if the inverse square law diminution of flux is not an issue. The original paper on which the NewScientist based its article is the preprint Sugawara, H., Hagura, H., Sanami, T. Destruction of Nuclear Bombs Using Ultra-High Energy ... 13 It actually can, through gravity. This is a mechanism some people use to explain why the dark matter density profile is not "cuspy" in dwarf galaxies. The idea is fairly simple: a super nova explodes, it pushes out gas. The gas is coupled through gravity with dark matter, so dark matter is also moved around. This changes the potential of the galaxy, which in ... 13 Iron comes from exploding white dwarfs and exploding massive stars(Wikipedia). (One of many amazing images by Cmglee ) Periodic table showing the cosmogenic origin of each element. Elements from carbon up to sulfur may be made in small stars by the alpha process. Elements beyond iron are made in large stars with slow neutron capture (s-process), ... 12 There are several main points that should clear this up: Supernova remnants include neutron stars, and supernova nucleosynthesis can occur in the supernovae producing those, too. I couldn't tell you what the relative yields are between these and the supernovae that produce black holes. However, the composition of the progenitor is mass-dependent, and this ... 12 Primary muons Muons can be produced in any sufficiently energetic event, but we don't ever see them directly. The issue is that—though they are long lived by the standards of particle physics—muons still only have a mean lifetime of about 2 microseconds ($\tau = 2.2 \times 10^{-6} \,\mathrm{s}$). The mean distance they can travel (when highly relativistic)... 10 The time delay between neutrinos and photons does not tell us directly about the absolute mass of the neutrinos. The time delay between a neutrino of mass$m$and a massless neutrino does: $$\Delta t = \frac{d}{v} - \frac{d}{c} \approx 0.5 \left(\frac{mc^2}{E}\right)^2 d,$$ where$\Delta t$is the time delay in seconds,$v \approx c[1-\frac{1}{2}\left(\...

9

http://profmattstrassler.com/2011/09/20/supernovas-and-neutrinos/ This website confirms what you said about the neutrinos from the 1987 supernova arriving before the light from the supernova. It doesn't specifically say which detectors detected the neutrinos. The reason the neutrinos reached earth before the light is not because the neutrinos were ...

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