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Solfe
2018-Jan-28, 03:54 AM
According to Wikipedia, GRB come from super or hypernovas. What would happen to a planet in orbit around that star? Would it be vaporized completely?

Second, is there a beam like quality to GRB like pulsars? Or does the energy go in every direction?

Jens
2018-Jan-28, 07:15 AM
Iím not sure about the first question, but on the second, I believe they are narrow beams, that go in two directions, 180 degrees apart.

trinitree88
2018-Jan-28, 10:49 PM
Jens. For jets, which originate some of the bursts, the beaming factor is about 10,000/ 1. ....pretty narrow.

antoniseb
2018-Jan-29, 11:45 AM
According to Wikipedia, GRB come from super or hypernovas. What would happen to a planet in orbit around that star? Would it be vaporized completely?
There are a number of situations that could give rise to a GRB. Black-hole-forming hypernovae are one. Merging neutron stars is another (for example). For the hypernovae, it should be pretty likely that the beams (however wide they are) will exit the star near the rotational poles of the star, and so far from any planets.

Assume for the moment that there is a planet in the habitable zone around one of the monster stars (lets use 1 billion km radius of orbit for easy computation, it would probably be further). Let's imagine that an Earth-sized planet is unlucky enough to have been previously perturbed into a polar orbit around the star, and is exactly in the middle of the beam when the core collapses. Let's say that the GRB beam produces 10^53 ergs of energy over its 10 second duration (plausible numbers) and that 10% beam's intensity is concentrated in a cone half a degree in diameter (plausible numbers). The beam at the orbit is about 10^15 square kilometers, and the planet is about 10^8 square kilometers of absorbing surface ... so the planet would get 10^45 ergs during the duration of the beam.
This is about 10^27 ergs per square cm of the star-facing surface of the planet.

The gamma rays come very quickly from one direction. They are a form of energy that can only penetrate about a meter or so of rocky material, and so what I suspect would happen (not running a simulation) is that the beam would vaporize the top meter of rock in about one attosecond (10^-18 seconds)... note that the speed of light would say it would require 3 nanoseconds to penetrate a meter, so the energy delivery initially a billion times what is required. However, it is worth considering whether the vapor/plasma from the first meters of rock will continue absorbing gamma rays, and act as a shield for the lower layers. I expect that these nuclei need to be accelerated by heat up to .01 c in order that they are removed by their own energy from the ablative absorbing area before time expires for the beam (10 seconds).

So, the speed of the particles goes up as the square root of temperature, and my guess says that it would take about 100 million degrees to get there. ... which this scenario easily exceeds in the three nanoseconds per meter of rock. So, just as a back of the envelope calculation, an Earth-sized planet would be turned into energetic plasma in under a 10th of a second in the beam at 1 billion kilometers.

trinitree88
2018-Jan-30, 08:34 PM
There are a number of situations that could give rise to a GRB. Black-hole-forming hypernovae are one. Merging neutron stars is another (for example). For the hypernovae, it should be pretty likely that the beams (however wide they are) will exit the star near the rotational poles of the star, and so far from any planets.

Assume for the moment that there is a planet in the habitable zone around one of the monster stars (lets use 1 billion km radius of orbit for easy computation, it would probably be further). Let's imagine that an Earth-sized planet is unlucky enough to have been previously perturbed into a polar orbit around the star, and is exactly in the middle of the beam when the core collapses. Let's say that the GRB beam produces 10^53 ergs of energy over its 10 second duration (plausible numbers) and that 10% beam's intensity is concentrated in a cone half a degree in diameter (plausible numbers). The beam at the orbit is about 10^15 square kilometers, and the planet is about 10^8 square kilometers of absorbing surface ... so the planet would get 10^45 ergs during the duration of the beam.
This is about 10^27 ergs per square cm of the star-facing surface of the planet.

The gamma rays come very quickly from one direction. They are a form of energy that can only penetrate about a meter or so of rocky material, and so what I suspect would happen (not running a simulation) is that the beam would vaporize the top meter of rock in about one attosecond (10^-18 seconds)... note that the speed of light would say it would require 3 nanoseconds to penetrate a meter, so the energy delivery initially a billion times what is required. However, it is worth considering whether the vapor/plasma from the first meters of rock will continue absorbing gamma rays, and act as a shield for the lower layers. I expect that these nuclei need to be accelerated by heat up to .01 c in order that they are removed by their own energy from the ablative absorbing area before time expires for the beam (10 seconds).

So, the speed of the particles goes up as the square root of temperature, and my guess says that it would take about 100 million degrees to get there. ... which this scenario easily exceeds in the three nanoseconds per meter of rock. So, just as a back of the envelope calculation, an Earth-sized planet would be turned into energetic plasma in under a 10th of a second in the beam at 1 billion kilometers.


Antoniseb. Yep & gamma rays have energies sufficient to produce more than a plasma of ions.....they'll nuclearly photodissociate the nuclei of the ions, following the curve of binding energy. Given sufficient flux, cross-sections, and time, Earth could become largely protons and electrons, all over again. pete