# Tag Info

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Believe it or not, this was actually a theory held back in the 1990's! Astronomers back then thought that GRBs were the direct result of anti-matter-matter collisions (between anti-matter comets and matter comets) that were taking place in the Oort cloud. This 1996 article by Chuck Dermer (paywall), titled Gamma-ray bursts from comet-antimatter comet ...

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Here is a thesis trying to fit the spectra of the observed gamma rays, and if you read the conclusions you will see that there are various sources. One has to distinguish antimatter as low in energy as a positron, which can also appear from decays of isotopes: The observed distribution of gamma rays is consistent with the standard picture where the ...

2

Your What happens in high-energy physics experiments aside partially contradicts your final question But if we restrict the discussion to radioactive decay, fusion in stars, cosmic rays, is everything a lepton, baryon, or a photon? Radioctive decay has as end products photons, leptons and baryons. Fusion and cosmic rays are the realm of ...

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But if we restrict the discussion to radioactive decay, fusion in stars, cosmic rays, is everything a lepton, baryon, or a photon? No. Baryons are not elementary particle, but are composed of 3 quarks bound by gluons. There is a class of particles called mesons, which consist of a quark and antiquark. The pion is an example of a meson. Pions are ...

2

The Earth and the Sun has magnetic fields which shields us from cosmic rays, as a charged cosmic ray particle will loose kinetic energy when its direction is perpendicular to the magnetic field. So what happens to the kinetic energy of the cosmic ray particle? According to the first law of thermodynamics it can't just disappear. It goes to the magnetic ...

1

Does it gain infinite momentum before it crosses the horizon? Momentum is frame dependent so, when asking for the momentum, one must specify according to whom? Since the Schwarzschild metric is independent of time, the time component of the four-momentum of freely falling particle is constant. $$p_0 = -E$$ Now, imagine that the particle is at some ...

1

It would be more correct to say that distant galaxies appear than to say they disappear. Based upon the accepted big bang theory, there are galaxies that formed early in the universe from which light has not yet reached us, but that will reach us in the future. On the other hand, accelerating expansion of the universe could cause light emitted after a ...

3

When you're asking a question about general relativity you need to state what coordinates you want to use. This isn't just a mathematical nicety - as you'll see shortly, the different coordinate systems attached to different observers will describe very different behviours. The obvious interpretation of your question is to ask what happens when an observer ...

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I have been researching the 1987A supernova personally and I can say through my study of supernova and particularly 1987A, time lapse in respect to peaks of brightness and naked eye, live observation is completely plausible, realistic and proven. I personally have been very hesitant in posting anything like this for fear of being ridiculed yet I was camping ...

4

Stars form from collapsing dust clouds, and since interstellar dust clouds are quite turbulent at interstellar length scales it is almost certain that the dust cloud forming the star will have a non-zero angular momentum, and hence the star will have a non-zero angular momentum i.e. it will be rotating. There are various ways we can measure the rotation of ...

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Rotating, although not necessarily at a uniform rate since a star is not a rigid body. A point on the Sun at the equator makes a full rotation relative to other stars in about 24 days. Further from the equator, the period is longer. Pulsars can make a full rotation in less than one second.

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The known exoplanets are not representive. Each discovery technique has its own bias. For the transit of star technique, the probabilty that a planet transits the star, as observed from a distance, is proportional to the radius of the star and inversely proportional to the orbital radius (semi-major axis). Also, below a certain size, there will be ...

3

To address the actual question of how we know the composition of UHECR without relying on source information (of which we have none), we have to look at their extensive air showers (EAS). After an UHECR hits the top of the atmosphere an EAS is created in the air, but p and Fe will create EAS with different shapes. Properties of hadronic interactions are ...

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This "bounce" theory isn't logical. 1. How strong that bounce must be so it can escape such strong gravity and eject very heavy outer layers of the core? 2. For something to bounce it must be elastic in some way or hit elastic surface. What is elastic in this case? 3. Another thing that's bothering me is what happens with bouncing when the core is much ...

1

The density of a black hole is defined simply as the mass within the event horizon divided by the volume within the event horizon. This gives an average density, but doesn't imply that the density is uniform within the event horizon. So when you hear statements like the density of a supermassive black hole is the same as water don't take this too literally. ...

3

You are a little confused in your stellar evolution model. After the ignition of hydrogen fusion in the core of a star, it will next progress to helium fusion, then to carbon/oxygen fusion via the triple-alpha process (I've skipped a lot of steps and details there, if you want the details you can look at either Hansen & Kawaler's Stellar Interiors text ...

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Matlab is faster than IDL and phyton. If you dont use linear algebra libraries It is also faster than fortran and C. You can try and see for yourself. There are some online matlab libs for astronomicsl image processing incliding treating FITS.

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