Star Mergers

[CarlNGraham]

Well the link below and the Wikipedia both agree that this is still a very much debated subject. I still didn't see where mainstream is leaning towards two white dwarfs merging though.

 

I am referring more to observational evidence, rather than the theory.

We have thousands of pictures of areas of space before a supernova event, as well as after.

So far there is very little evidence for the other star before or after the event.

 

This suggest only one star was involved or both were totally destroyed, possibly in a collision.

 

Many remnants are not symmetrical, possible suggesting two slightly diffent size stars were involved.

 

In theory, a white dwarf gaining mass by any method could cause a supernova.

 

I like the idea of dense interstellar medium trapping shells of matter expelled by the star in the red giant phase, and then this latter falling back onto the white dwarf phase.

[Lancewen]

I am referring more to observational evidence, rather than the theory.

We have thousands of pictures of areas of space before a supernova event, as well as after.

So far there is very little evidence for the other star before or after the event.

 

This suggest only one star was involved or both were totally destroyed, possibly in a collision.

 

Many remnants are not symmetrical, possible suggesting two slightly diffent size stars were involved.

 

In theory, a white dwarf gaining mass by any method could cause a supernova.

 

I like the idea of dense interstellar medium trapping shells of matter expelled by the star in the red giant phase, and then this latter falling back onto the white dwarf phase.

 

As I understand white dwarf matter, the atoms still have electron shells, but they are highly compressed and are very close to the nucleus. The Chandrasekhar limit is the point at which the electron pressure fails and those electrons collapse into the nucleus changing the protons into neutrons. So if you add enough mass to a white dwarf star and it goes over the Chandrasekhar limit, the result should be a new neutron star and not a supernova. I believe that's why it is believed that white dwarfs steal mass more slowly so that as they approach the Chandrasekhar limit they have a chance to destabilize into a supernova before they go over the Chandrasekhar limit.

 

 

If there's another theory taking shape about type 1A's, could you please post the details or explain why the standard theory is showing strain? Are scientists starting to believe the Chandrasekhar limit doesn't work as expected?

 

[CarlNGraham]

As I understand white dwarf matter, the atoms still have electron shells, but they are highly compressed and are very close to the nucleus. The Chandrasekhar limit is the point at which the electron pressure fails and those electrons collapse into the nucleus changing the protons into neutrons. So if you add enough mass to a white dwarf star and it goes over the Chandrasekhar limit, the result should be a new neutron star and not a supernova. I believe that's why it is believed that white dwarfs steal mass more slowly so that as they approach the Chandrasekhar limit they have a chance to destabilize into a supernova before they go over the Chandrasekhar limit.

 

 

If there's another theory taking shape about type 1A's, could you please post the details or explain why the standard theory is showing strain? Are scientists starting to believe the Chandrasekhar limit doesn't work as expected?

 

 

I think you are interested in the theory, where as I am concentrating on observational evidence (not quite fact :) ).

 

I may not be up to date on this, but so far not one has found the other star (apart from possibly Tycho G)

I think there are a good 5 to 7 near enough, to be observed in detail where no other star can be detected to a high degree of certainty.

 

So in the cases observed in detail, either the second star was so close to the explosion that it was destroyed without a trace, ie a collision, or only one star was involved.

[Lancewen]

I think you are interested in the theory, where as I am concentrating on observational evidence (not quite fact :) ).

 

I may not be up to date on this, but so far not one has found the other star (apart from possibly Tycho G)

I think there are a good 5 to 7 near enough, to be observed in detail where no other star can be detected to a high degree of certainty.

 

So in the cases observed in detail, either the second star was so close to the explosion that it was destroyed without a trace, ie a collision, or only one star was involved.

 

Actually I'm interested in theory supported by observations. What's your evidence that these supernova events are in fact type 1A. Another thing you should consider about type 1A supernovas is they are all very close to identical in brightness. At least that's the claim as to why they can be used to estimate distance. That would seem to indicate a single type event causes a type 1A supernova every time. If it can be shown that observations are not supporting the theory, there will be many other things that will have to be reconsidered.

 

I see a lot that I think is wrong with the current BB theory. So I don't have a problem re-examining theory that doesn't match or support observation.

[maddog]

As I understand white dwarf matter, the atoms still have electron shells, but they are highly compressed and are very close to the nucleus. The Chandrasekhar limit is the point at which the electron pressure fails and those electrons collapse into the nucleus changing the protons into neutrons. So if you add enough mass to a white dwarf star and it goes over the Chandrasekhar limit, the result should be a new neutron star and not a supernova. I believe that's why it is believed that white dwarfs steal mass more slowly so that as they approach the Chandrasekhar limit they have a chance to destabilize into a supernova before they go over the Chandrasekhar limit

That is my understanding as well (at least most of the electrons - some atoms might be highly ionized). I don't the Chandrasekhar limit is so much in question. It might be that the momentum (angular and moment of inertia) might come into play at augmenting the value slightly.

Again I would think this would be only for high velocity stars. More sedate trajectories would like create orbits instead.

 

If there's another theory taking shape about type 1A's, could you please post the details or explain why the standard theory is showing strain? Are scientists starting to believe the Chandrasekhar limit doesn't work as expected?

I am not aware of anything new regarding 1A's. Though I might have missed it. I do sometimes.

 

maddog

[CarlNGraham]

I suspect the Type 1a supernova are caused by the Chandrasekhar limit being exceeded, either by Collison or slow transfer.

 

I am only saying, merging or colliding anything with a cooling white dwarf is highly likely to cause an explosion.

The atoms are just too tightly packed for electrons to exist in shells around the atoms, adding more mass will cause total collapse.

 

Another complication when thinking about star mergers, is some stars like Betelgeuse possibly have more than one core.

That is it has a possible companion star orbiting inside it.

Wikipedia