33 votes

Why are there no gamma-ray bursts detected in our galaxy?

All models of gamma-ray bursts involve extremely energetic phenomena: particular types of supernovae, the coalescence of binary compact objects, strong magnetar flares, or tidal disruption events. It ...
  • 34.2k
28 votes

What's the percentage of strange matter inside a star at any time?

Zero. Normal stars are not dense enough to produce strange matter. They have regular matter only (neutrons and protons). Strange matter has been hypothesized to form inside neutron stars, but this is ...
  • 4,164
23 votes

How can astronomers pinpoint the location of the source of a neutrino?

You correctly state that neutrinos do not interact too often. The physical parameter describing that is the effective cross-section. So what you observe in a detector is not the neutrino itself, but ...
  • 5,334
10 votes
Accepted

What's the percentage of strange matter inside a star at any time?

Let me first underline two specific definitions of @Alexandre: We are looking for "matter", that means a finite region in space in thermal equilibrium. And we are looking for "...
  • 116
9 votes

Amount of energy of the Big Bang

Let's start by making some points clear: 1. We don't know what the Big Bang was. Rather, we know that the Universe is expanding. If you extrapolate backwards, you'd expect the Universe to be denser ...
9 votes

How can astronomers pinpoint the location of the source of a neutrino?

High energy muon neutrinos occasionally interact and produce a muon. Energy and momentum must be conserved in the process and the muon heads off in the same direction as the neutrino. The relativistic ...
  • 120k
8 votes

Why is the number of Long Gamma Ray Burst (LGRB) event occurrences greater than the number of Short Gamma Ray Burst (SGRB) event occurrences?

Long and short GRBs are thought to arise from different types of event, involving different types of star. Therefore the question you should be asking is why are their event rates so similar?! Long ...
  • 120k
7 votes

Does a gravitational wave loses energy over distance?

tl;dr: Yes. Feynman's beads on a string argument The other answers skirt what I think is the issue that the OP is asking about. In a lossless medium a spherical wave packet itself, caused by a ...
  • 30.6k
6 votes

How can a singularity rotate?

There are multiple solutions to general relativity which allow for multiple different types of black holes. The "normal" black hole you see most people talk about, with a zero-volume, point ...
  • 14.5k
6 votes
Accepted

What type of energy is escaping from black-hole's poles?

The article you've read is not quite accurate/correct. A more correct pictue is as follows: A star may approach a super-massive black hole (SMBH) so closely that the tidal forces of the SMBH tear it ...
  • 5,306
6 votes
Accepted

What does it mean for something to be optically thick to pair production?

In astrophysics, being "optically thick" means that light (and it is applied to photons of any frequency, not just visible light) cannot travel across or out of a body (which may be the ...
  • 120k
5 votes

On (minuscule) dark matter production in supernovae

There are several types of supernova and ways that the core can collapse. Lets take an extreme case in which gamma-ray photodisintegration destroys all of the heavy elements (Si, Fe and Ni, etc) and ...
  • 2,857
5 votes

Energy needed to create a black hole vs energy needed to run the Large Hadron Collider?

Your question touches on a few points. First, yes, he was flippant, but the risk was super-low. The simplest way to explain this is that nothing happens in CERN that doesn't happen all over the ...
  • 22.9k
4 votes
Accepted

What is the bulk Lorentz factor?

I think it is referring to the speed and Lorentz factor $(\beta = v/c$ and $\gamma = [1-\beta^2]^{-1/2})$ of the gas as a whole. Within the gas, there could be particles moving with a variety of ...
  • 120k
4 votes
Accepted

Compton scattering of high energy radiation

The answer is pair production. Once photon energies exceed 1.02 MeV it is possible to spontaneously create an electron-positron pair in the presence of an atomic nucleus (to conserve momentum). In ...
  • 120k
4 votes

How can a singularity rotate?

Don't think of the singularity as being an object made of matter. A black hole is a vacuum solution to the relativity equations. That means there is nothing inside the black hole. A black hole ...
  • 93.7k
4 votes
Accepted

Non-thermal Sunyaev-Zel'dovich effect

The non-thermal S-Z effect is caused by inverse Compton scattering of the CMB photons from a non-thermal population of electrons - i.e. electrons that have high energies not because they are hot, but ...
  • 120k
4 votes

Do the newly-created deuterons in our Sun release any photons? In addition to a positron and an electron neutrino?

Does the newly-formed deuteron then automatically release a photon? Not directly. The initial step of the p-p chain is a weak interaction rather than an electromagnetic interaction. This initial step ...
  • 28.7k
3 votes
Accepted

Higgs Field inside a White Dwarf

In a word, no. The universe was certainly quite hot for the first few hundred thousand years, but most of the important events of the Big Bang happened in the first few seconds, when the universe was ...
  • 10.5k
3 votes

What is Propeller Effect exactly?

The magnetic field of the rapidly rotating neutron star interacts with the material coming from the other star in the binary. This results in a transfer of angular momentum, spinning the neutron star ...
  • 7,384
3 votes

How can a singularity rotate?

One way to think of a black hole is that it is what is left behind when some matter (or energy) collapses so far that an event horizon forms. After that, no information of any kind can get out past ...
  • 9,928
3 votes
Accepted

How does the Gamma Ray Burst that occurred when 2 black holes merged compare to other GRB's?

The interpretation you suggest in the second paragraph is incorrect. It is understandable, since there is a debate in the literature - different papers come to potentially contradicting conclusions. ...
3 votes

meaning of p-wave charmonia

You're correct that "$p$-wave" in this context means that the charmonium has orbital angular momentum $L=1$. The principal observable effect is that two-particle states with even $L$ have even parity, ...
  • 971
3 votes

Do the newly-created deuterons in our Sun release any photons? In addition to a positron and an electron neutrino?

No, deuteron production doesn't directly release a photon. Of course, when the positron annihilates with a nearby electron, that creates some gamma photons. As David Hammen mentions, the proton-...
  • 10.5k
2 votes

Energy needed to create a black hole vs energy needed to run the Large Hadron Collider?

According to our current understanding, there is no lower bound for the energy needed to make a black hole. Any object, no matter how small, if compressed enough, could in theory form a black hole. ...
2 votes
Accepted

In what units to quote the thermal Blackbody temperature

I'm not entirely sure what you mean, but the (Planck's) formula for blackbody radiation is given by $$S_{\lambda} = \frac{8 \pi h c}{\lambda^5} \frac{1}{e^{hc/\lambda kT} - 1}$$ where $h$ is in $\...
2 votes

On (minuscule) dark matter production in supernovae

Your line of thought is tempting and nice to read. But do not neglect that in particular the typical WIMP mass range 1...100GeV is highly challenged by direct dark matter experiments and also LHC: ...
2 votes

Does a gravitational wave loses energy over distance?

In empty space, just like a light wave, they spread out, becoming less intense as they get further from their source, but never vanishing completely. At some stage the waves from a distant event might ...
  • 9,928
2 votes
Accepted

What powered the Big Bang?

This is a difficult question to answer. Physics really starts after the big bang. Scientist don't know about the laws, if any, before the first instance after the big bang. The time before and during ...
  • 4,346
1 vote
Accepted

Comparing Star Formation rate in different galaxies

Not being an expert in star formation, I found a well-written paper summary from which I conclude that typical star formation rates range between $6 \ldots 24 M_\odot / yr$. The blog quotes the ...
  • 5,334

Only top scored, non community-wiki answers of a minimum length are eligible