# Tag Info

61

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 ...

40

There are lots of possible ways that stars can end their life, even in the subset of cases where the end is violent. Eloff has given an excellent answer, but I wanted to add a few points. Summary (tl;dr): You need the right conditions (mass, angular momentum, metallicity, etc) to produce a proto-neutron-star which is able to resist complete collapse to a ...

36

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 ...

31

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 ...

24

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 ...

21

Depends on the detection technology. Yes Cerenkov based detectors (SNO and Super-Kamiokande for instance, as well a many cosmic ray neutrino detector) are direction sensitive, and this is one of the design considerations that drive the use of this tricky technique. The best results come from quasi-elastic reactions like $\nu_l + n \to l^- + p$. The ...

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

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 ...

15

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; http://adsabs.harvard.edu/abs/2012ApJ...757...55O ). Update - ...

15

The calculation is done for 1987A here. Basically, the neutrinos' fractional speed increase from the new paper is $2.48\pm0.28\pm0.30\times10^{-5}$ (statistical / systematic errors, respectively) . SN1987a was $166\,912\pm10.1$ ly away, so multiplying the fraction by the travel time gives $4.14\pm0.97$ years. In reality, we got the neutrinos a few hours ...

14

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 ...

13

None of those stars can go supernova, so the question is rather moot. If you look at the classifications, the most luminous is Sirius A (an A sequence star even) you can get an idea of its mass. If you look at your source page, and link to the explanation you see that A stars range from 1.4 to 2.1 stellar masses. In order to go supernova though, you need ...

12

Supernovae can take well over a week to reach maximum luminosity, and they stay rather bright for months after the peak. This just goes to show how much energy is involved in these event. I was going to assemble a collage of light curves from my own research, but then I realized this has already been done at Wikimedia Commons: These are rather idealized ...

11

What you are looking for is called the stellar mass function by astronomers. It is the distribution of masses for stars. There is a nice review of the definitions, measurements, and basic theory in Galactic Stellar and Substellar Initial Mass Function, Chabrier 2003, PASP 115 763. It discusses both the initial mass function (IMF) and the present-day mass ...

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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 nucleons can then form new elements. Nakamura & Shigeyama (2004) were able to calculate yields for 6Li, 7Li, and isotopes of Beryllium and ...

10

You have to run a massively sophisticated supernova simulation to get that kind of data. Whole research groups work on them. The biggest unknowns are generally the details of neutrino physics. This is both because neutrino hard data doesn't come easy, and because solving the radiation field of a supernova is a function of seven or eight variables (x, y, z ...

10

The short answer is probably "yes we can", and possibly "we've already seen supernovae from the first galaxies", in the form of long-duration gamma-ray bursts. GRB 090429B has been given a redshift z=9.4, beating the previous record-holder GRB 090423 at z=8.2. As we continue to watch the skies, we're seeing more and more of these objects, and we'll gradually ...

9

In answer to your question of "What happens to the neighboring star?", according to the Johns Hopkins folks, it gets blown away: (Credit Johns Hopkins) I would be a little skeptical of the certainty of this claim only because we have not been able to observe any of these Type Ia explosions up close while it is happening. That's why the Type Ia SN 2011fe is ...

9

You're correct that when fusion reactions decrease past a certain point because the fuel is used up, the outward pressure created by the fusion no longer counteracts the gravitational forces and the star collapses (rapidly) in on itself. In stars of the right mass (smaller than about 15 solar masses, but large enough to collapse into a neutron star) the ...

9

Very simply put, in order to view any event twice, both occasions in absolute real time (ignoring the time the light took to reach you, directly from the event), you would need to outrun the photons, which entails faster-than-light travel. Now, if you're willing to accept less than real time, it is absolutely possible, though it gets less and less practical ...

8

How do I stay alive to be killed by neutrinos? You wouldn't. The point is being made that even the beam of neutrinos with a supernova at one astronomical unit distance would be intense enough that enough of them would interact with the matter of your body to be lethal. So even the neutrinos would get you if all the other stuff - notably $\gamma$s didn't. ...

8

It's interesting you found Tycho as an example as this was one of the early recorded supernovas back in 1572...by Tycho of course. This is considered a Type Ia Supernova and the image you reference isn't really how it looks. That's a modified composite to visualize the microwave and infrared components of the remains together. As Kyle mentioned, you can ...

8

The biggest thing about this supernova is how CLOSE it is. A mere 21 million light years away (as opposed to being a billion light years away). The folks at John Hopkins think that studying a ype Ia supernova is valuable for several reasons. SNe Ia are also very bright compared to other standard candles, which means they can be seen at high redshifts ...

6

Be careful when trying to intuit how sensitive the integral formulation is to changes in $w$. The equation of state parameter only enters as part of the exponent of $1+z$, so for $z \approx 0$, $w$ has approximately no effect: $1^0 \approx 1^\epsilon$. To illustrate with equations, suppose you already know $\Omega_\mathrm{M}$ and $\Omega_\mathrm{DE}$ ...

6

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 ...

6

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 ...

6

Star are fighting against gravitational forces by pressure gradients due to fusion in the core (and the shells outwards). Once fusion stops, there is no pressure gradient and gravity wins the "battle." The classic picture of a massive star at the end of its life is (and obviously not to scale), But each star star started off with just hydrogen in the ...

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