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Author Topic: Are supernovas not omnidirectional?  (Read 2013 times)

Offline Jybwee

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Are supernovas not omnidirectional?
« on: 10/03/2015 12:08:48 »
Was clicking through youtube when i happened on a video where they talked about Betelgeuse going supernova. Brain Cox was in the video and said if it was pointed in our direction when going supernova it would wipe us out but it is spinning away from us.

I couldn't understand why a supernova wouldn't explode out in all directions. I suppose it makes sense that it's not a perfect explosion from it's exact center in all directions evenly, but he makes it sound that it is pointed in such a way that makes a huge change in how the blast... releases? Why? :) Is there an easy way to explain that? If the earth went supernova (just for a fun example) would the energy blast out more from the poles? or the opposite?

I'm over here looking at pictures of the Crab nebula and Kepler... the 'flatness' of our solar system... something just isn't connecting. Someone save me!


 

Offline evan_au

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Re: Are supernovas not omnidirectional?
« Reply #1 on: 10/03/2015 18:18:08 »
It's not a supernova (yet), but Eta Carinae had a spectacular nova, observed in the early 1800s.

Through a telescope, the debris appears to be shaped like a dumbbell (or hourglass for the more mature), with an explosion out both ends (the poles?), but less debris around the middle (the equator?).

This may be due to gas puffed off the bloated star, forming an equatorial belt which then acts as a partial shield against debris from the (super)nova? Eta Carinae is a binary star, and the orbital axis of the two stars may also affect the shape of the explosion.

It should be possible to detect the orientation of a star relative to us by spectroscopic means. If we are looking at the equator, we should see more red and blue shift than if we are looking down on a pole.

The processes that go in in a supernova are complex, and have so far defeated accurate modelling on even our most powerful supercomputers.

But perhaps Brian Cox was not talking about the supernova itself, but the beams of relativistic particles which seem to shoot out the poles of the accretion disk around the resulting black hole?
 

Offline evan_au

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Re: Are supernovas not omnidirectional?
« Reply #2 on: 10/03/2015 19:19:02 »
PS: Some other considerations:

As a star collapses to neutron star densities (and beyond, towards a black hole), its magnetic field is compressed into a very small volume.
This results in very intense magnetic fields, which may direct some of the debris in the resulting supernova explosion?

Angular momentum must also play a part. When the core of the star can no longer withstand the pressure of the overlying matter, it collapses inwards. The angular momentum of the equatorial gas would prevent it collapsing very far. However, the gas near the poles has less angular momentum, and so would collapse more rapidly, initially creating a donut shape for the star. It might then explode more rapidly out of the "empty" ends.

Much of the energy carried out of the core of the imploding star is in the form of neutrinos, which are immune to the magnetic field. I would expect neutrinos to carry off energy equally in all directions...
« Last Edit: 10/03/2015 19:41:24 by evan_au »
 

Offline Jybwee

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Re: Are supernovas not omnidirectional?
« Reply #3 on: 13/04/2015 00:23:12 »
Sorry it has taken some time to reply but i have had this in my mind for some time. Your replies were definitely a HUGE step forward in understand underlying principles at work.

I took a bit of time (not much to spare in my current lifestyle) to study explosions. Never really satisfied by what i've learned there.

Today a friend linked me this and i thought it would be a nice addition to anyone wondering the same -
 

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Re: Are supernovas not omnidirectional?
« Reply #3 on: 13/04/2015 00:23:12 »

 

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