If two white-dwarf stars combined together,there will be supernova?which type?-

[magnetar]

If two white-dwarf stars combined together,there will be supernova?which type?---

(1)If two white-dwarf stars combined together,there will be supernova? which type?

(2)If two neutron stars combined together ,there will be supernova?

(3)If a white-dwarf and a neutron star combined together ,there will be supernova?

Thank you in advance!

 

[Wallace]

In all cases I suspect the answer would be yes however the question is how these collisions would occur? Stars not associated with each other (i.e. not a binary system) almost never collide, there is simply to much space between stars for there to be a reasonable chance that they will ever collide.

Interactions between stars in a binary system do lead to supernovae, usually when once star expands while in its red giant phase and sheds some material onto the companion star. Two white dwarves and/or neutron stars orbiting one another will have no way to exchange any mass or collide since the orbit is stable and they are in their final stage of evolution.

 

[magnetar]

Two white dwarves and/or neutron stars orbiting one another will have no way to exchange any mass or collide since the orbit is stable and they are in their final stage of evolution.

Accordong to GR,this system will emit gravitational wave ,so they will gradually approach each other, finally they combind together!

 

[Wallace]

Oh yes, good point!

I'm no expert on this but I would imagine the rate at which they lose energy and spiral inwards would be pretty slow such that I would be surprised if the Universe was old enough for any pairs of Neutron stars to have spiraled in sufficiently to do this. I may well be wrong though, but that would be my suspicion.

 

[magnetar]

I would be surprised if the Universe was old enough for any pairs of Neutron stars to have spiraled in sufficiently to do this

You can login this website ,you will find the answer http://www.astro.cornell.edu/academics/courses/astro201/psr1913.htm

The pulsar's orbit is shrinking with time as shown in this diagram; currently, the orbit shrinks by about 3.1 mm per orbit. The two stars should merge in about 300 million years from now.

(Figure from Weisberg et al. 1981)

 

[Wallace]

Looks like the orbits shrink a lot quicker than I expected. I guess they may well cause some kind of SN when they merge then.

I should stick to answering the question that I know the answer to

 

[tony873004]

A neutron star is almost dense enough to be a black hole. I wonder if there is a point where a neutron star and a companion would spiral close enough to each other, without colliding, where their combined gravity can form an event horizon, sparing the universe the fate of being bathed in the awesome radiation emitted if they ever did collide?

 

[magnetar]

A neutron star is almost dense enough to be a black hole. I wonder if there is a point where a neutron star and a companion would spiral close enough to each other, without colliding, where their combined gravity can form an event horizon, sparing the universe the fate of being bathed in the awesome radiation emitted if they ever did collide?

Although this event is powerful, if the distance is farther enough ,we are all very safe !