When will Betelgeuse explode

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Message 1840569 - Posted: 7 Jan 2017, 8:14:23 UTC - in response to Message 1840549.  

In the 1987 supernova event neutrinos arrived before photons, not because they are faster but because photons take a longer time traversing the core of the star.
Tullio

Yes. But a supernova is not a star. It was a star and the core is gone.
All photons in the former star can move more freely in such event.
Photons interact with matter where as neutrinos doesn't do that so often so maybe there will be a time delay.
But I doubt that the time delay will differ so much in a supernova.
BTW The photons take thousands of years to "fight" their way to the surface of the Sun but only about 8 minutes to hit earth when released.
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Message 1840660 - Posted: 7 Jan 2017, 17:33:53 UTC - in response to Message 1840569.  

In the 1987 supernova event neutrinos arrived before photons, not because they are faster but because photons take a longer time traversing the core of the star.
Tullio

Yes. But a supernova is not a star. It was a star and the core is gone.
All photons in the former star can move more freely in such event.
Photons interact with matter where as neutrinos doesn't do that so often so maybe there will be a time delay.
But I doubt that the time delay will differ so much in a supernova.
BTW The photons take thousands of years to "fight" their way to the surface of the Sun but only about 8 minutes to hit earth when released.

The explosion isn't a detonation and actually would be better described as an implosion. It happens at the core of the star. It takes some time for the rest of the star to become aware that the core has changed. The photons (and matter) made at the core still have to travel to the surface through the rest of the star. The pressure shock waves that tear the outer layers away must travel at less than the speed of light as they are matter. The neutrinos which don't interact with anything else thus get a good head start. The first light we likely see is when the shock wave reaches the surface and causes the hydrogen there to fuse by compression. The photons from the core are still fighting their way out.
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Message 1840677 - Posted: 7 Jan 2017, 18:49:16 UTC - in response to Message 1840660.  

In the 1987 supernova event neutrinos arrived before photons, not because they are faster but because photons take a longer time traversing the core of the star.
Tullio

Yes. But a supernova is not a star. It was a star and the core is gone.
All photons in the former star can move more freely in such event.
Photons interact with matter where as neutrinos doesn't do that so often so maybe there will be a time delay.
But I doubt that the time delay will differ so much in a supernova.
BTW The photons take thousands of years to "fight" their way to the surface of the Sun but only about 8 minutes to hit earth when released.

The explosion isn't a detonation and actually would be better described as an implosion. It happens at the core of the star. It takes some time for the rest of the star to become aware that the core has changed. The photons (and matter) made at the core still have to travel to the surface through the rest of the star. The pressure shock waves that tear the outer layers away must travel at less than the speed of light as they are matter. The neutrinos which don't interact with anything else thus get a good head start. The first light we likely see is when the shock wave reaches the surface and causes the hydrogen there to fuse by compression. The photons from the core are still fighting their way out.

It's from my understanding that a supernova starts with an implosion that moments later make an explosion.
"Later" is probably less than a minute because that the atoms are imploding at a very high speed into the center of the star.
I think 50% to 60% of the speed of light.
When it explode the star will lose much of it's gravity so photons can move almost travel just as free as neutrinos.
But maybe i'm missing something...
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Message 1840797 - Posted: 8 Jan 2017, 7:27:34 UTC - in response to Message 1840677.  

In the 1987 supernova event neutrinos arrived before photons, not because they are faster but because photons take a longer time traversing the core of the star.
Tullio

Yes. But a supernova is not a star. It was a star and the core is gone.
All photons in the former star can move more freely in such event.
Photons interact with matter where as neutrinos doesn't do that so often so maybe there will be a time delay.
But I doubt that the time delay will differ so much in a supernova.
BTW The photons take thousands of years to "fight" their way to the surface of the Sun but only about 8 minutes to hit earth when released.

The explosion isn't a detonation and actually would be better described as an implosion. It happens at the core of the star. It takes some time for the rest of the star to become aware that the core has changed. The photons (and matter) made at the core still have to travel to the surface through the rest of the star. The pressure shock waves that tear the outer layers away must travel at less than the speed of light as they are matter. The neutrinos which don't interact with anything else thus get a good head start. The first light we likely see is when the shock wave reaches the surface and causes the hydrogen there to fuse by compression. The photons from the core are still fighting their way out.

It's from my understanding that a supernova starts with an implosion that moments later make an explosion.
"Later" is probably less than a minute because that the atoms are imploding at a very high speed into the center of the star.
I think 50% to 60% of the speed of light.
When it explode the star will lose much of it's gravity so photons can move almost travel just as free as neutrinos.
But maybe i'm missing something...

Gravity doesn't slow a photon down, it just makes it red. Hitting an atom "slows" them down as they change direction. As the density of atoms in the middle of a star is pretty big, the path the photon takes to the surface is light years long, it isn't a straight line out, as a neutrino takes.
As the star expands the density drops and the path length of the photos decrease. I'm sure there are papers with the math, but I'd still expect that the neutrinos get a dozens of minutes heard start. Unless we are talking about a galaxy half way across the universe, the neutrinos will beat the photons. It seems their speed difference is small, 1 part in 10^-9
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Message 1840832 - Posted: 8 Jan 2017, 16:11:33 UTC - in response to Message 1840797.  

It looks like the neutrinos win the race against the photons.
But not so much.
After travelling 168,000 light-years the neutrinos won by 3 hours.
https://en.wikipedia.org/wiki/SN_1987A#Neutrino_emissions
Approximately two to three hours before the visible light from SN 1987A reached Earth, a burst of neutrinos was observed at three separate neutrino observatories. This is likely due to neutrino emission, which occurs simultaneously with core collapse, but preceding the emission of visible light. Transmission of visible light is a slower process that occurs only after the shock wave reaches the stellar surface
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Message boards : Science (non-SETI) : When will Betelgeuse explode


 
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