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mugaliens
2010-Jul-28, 03:10 AM
...run simulations on what would happen in response to a collision between two stars or celestial masses, of any type (brown dwarf, black hole, white dwarf, MACHO, neutron star, etc.) to see if the result would look anything like the Homunculus Nebula (http://en.wikipedia.org/wiki/Homunculus_Nebula)?

This thread is for asking what has/has not been done.

swampyankee
2010-Jul-29, 01:46 AM
There's a few movies here (http://archive.ncsa.illinois.edu/Cyberia/NumRel/MoviesEdge.html). Google "numerical relativity" and you'll get a few hits. You may find some stellar collisions here (http://terpsichore.stsci.edu/~summers/viz/scviz/).

forrest noble
2010-Jul-29, 05:24 PM
mugaliens,

Hey Mugs, nice to see this interesting question.
There seems to be less theory concerning colliding stars on the net than one might expect, probably the reason for your question. Thought the link below was interesting concerning type 1a supernova and white dwarf collisions. Since I can find no links that I think could relate better to your question about the Homunculus Nebula than the link you provided, my guess is that colliding stars could run the gamut concerning explosion variations and the resultant ejected materials which could seemingly form nebulae of all different sizes, maybe dependent on the types of stars, ages, masses, angle of approach, relative velocities, etc. The clue in your link is that they believed the Homunculus Nebula was formed by an explosion close in magnitude to a supernovae type explosion. I think your collision guess seems like the most likely answer to me too. The most likely collision would seemingly be binary star collisions of some kind since binary and ternary systems are so common.

quote from the link below.

That leaves open the possibility of two different kinds of Type 1a supernovas (explosions) at loose in the universe and could add extra uncertainty into efforts to use exploding stars as standard candles to make precise measurements of the universe. Accreting white dwarfs go off at a precisely determined mass known as the Chandrasekhar limit, but a pair of colliding dwarfs could have a range of masses.

bold added

http://www.nytimes.com/2010/02/23/science/space/23star.html

neilzero
2010-Aug-01, 04:14 AM
Since a neutron star or quark star (if any) are much smaller and denser than a main sequence star, My guess is the compact star would pass though (even the center) of a main sequence star and keep going at only slightly reduced speed. Perhaps a significant amount of hydrogen and helium would follow the projectile out of the exit hole. Perhaps even a white dwarf would behave in this manner if the approach speed was high enough relative to the main sequence star? Neil

Nereid
2010-Aug-01, 04:28 AM
Since a neutron star or quark star (if any) are much smaller and denser than a main sequence star, My guess is the compact star would pass though (even the center) of a main sequence star and keep going at only slightly reduced speed. Perhaps a significant amount of hydrogen and helium would follow the projectile out of the exit hole. Perhaps even a white dwarf would behave in this manner if the approach speed was high enough relative to the main sequence star? Neil
IIRC, that's exactly what the simulation show: the compact object emerges with barely any evidence of the havoc it has wrought, said havoc including the complete destruction of the main sequence star.

In 2004, Scientific American had an issue which included an article by Michael Shara called "When Stars Collide". IIRC, it includes a discussion of the results of simulations of stellar collisions, between the full gamut of star types (main sequence, white dwarfs, neutron stars, even stellar-mass black holes); here's a link to its abstract (http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssuePreview&ARTICLEID_CHAR=229C315E-2B35-221B-6B3680DB0002D522)(the article itself is behind a paywall).

mugaliens
2010-Aug-01, 06:36 AM
mugaliens,

Hey Mugs, nice to see this interesting question.

Thanks - I'm looking!


There seems to be less theory concerning colliding stars on the net than one might expect, probably the reason for your question. Thought the link below was interesting concerning type 1a supernova and white dwarf collisions. Since I can find no links that I think could relate better to your question about the Homunculus Nebula than the link you provided, my guess is that colliding stars could run the gamut concerning explosion variations and the resultant ejected materials which could seemingly form nebulae of all different sizes, maybe dependent on the types of stars, ages, masses, angle of approach, relative velocities, etc. The clue in your link is that they believed the Homunculus Nebula was formed by an explosion close in magnitude to a supernovae type explosion. I think your collision guess seems like the most likely answer to me too. The most likely collision would seemingly be binary star collisions of some kind since binary and ternary systems are so common.

quote from the link below.


bold added

http://www.nytimes.com/2010/02/23/science/space/23star.html

I'd have to stop you with: ...my guess is that colliding stars could run the gamut concerning explosion variations and the resultant ejected materials which could seemingly form nebulae.

Beyond that, I'm awaiting a clue.

neilzero
2010-Aug-01, 08:35 AM
Michael Shara seems to have excellent credentials, so I suppose I should not disagree, but, much less than 600 kilometers per second seems more likely and the shock waves should propagate mostly in the direction of travel of the white dwarf. If so, a beam of gamma rays should come straight out of the exit hole, carrying away most of the energy released by the accelerated fusion of hydrogen and helium, plus some additional matter that will fuse in the beam. Perhaps 1% of the additional energy is sufficient to change our Sun to a red giant (over the next 50,000 years) but blown apart seems unlikely, especially if the path though our sun misses the core of our sun. The white dwarf surface will get much hotter if it is illuminated by the beam during departure from our solar system. What do you think? Neil

Nereid
2010-Aug-01, 09:05 AM
Michael Shara seems to have excellent credentials, so I suppose I should not disagree, but, much less than 600 kilometers per second seems more likely and the shock waves should propagate mostly in the direction of travel of the white dwarf. If so, a beam of gamma rays should come straight out of the exit hole, carrying away most of the energy released by the accelerated fusion of hydrogen and helium, plus some additional matter that will fuse in the beam. Perhaps 1% of the additional energy is sufficient to change our Sun to a red giant (over the next 50,000 years) but blown apart seems unlikely, especially if the path though our sun misses the core of our sun. The white dwarf surface will get much hotter if it is illuminated by the beam during departure from our solar system. What do you think? Neil
Perhaps taking a more detailed look at the simulations which Shara has based his article on would be a good idea?

IIRC, I read the full article, when the issue of Scientific American hit the newstands, and - to take just one example - 600 km/s is a quite robust estimate; don't forget that the Sun and any star it is about to collide with will accelerate towards each other. So, if two solar-mass objects start from rest, several light-years apart, and there is no other gravitational source to worry about, at what speed would they collide (assuming only Newtonian gravity)?

The point is, the simulations have been done, and Shara has reported the results of such.

Nereid
2010-Aug-01, 10:38 PM
mugaliens,

Hey Mugs, nice to see this interesting question.
There seems to be less theory concerning colliding stars on the net than one might expect, probably the reason for your question. [...]
I do not know what you had expected to find, but five minutes searching using ADS turned up hundreds of published papers on the topic.

For example, this one - "Three-dimensional hydrodynamical simulations of stellar collisions. I - Equal-mass main-sequence stars (http://adsabs.harvard.edu/abs/1987ApJ...323..614B)" - from 1987 (!) has been cited 160 times (according to ADS).

astromark
2010-Aug-02, 12:05 AM
Why haven't they... they have...


...run simulations on what would happen in response to a collision between two stars or celestial masses, of any type (brown dwarf, black hole, white dwarf, MACHO, neutron star, etc.) to see if the result would look anything like the Homunculus Nebula (http://en.wikipedia.org/wiki/Homunculus_Nebula)?

This thread is for asking what has/has not been done.

I find it interesting that the ETA CARINAE event of 1841 and its cloud of nebulocity The Homologous... gets entangled into this question.

( Homunculus )?,... regardless of the fact its not believed to be the result of any collision event. Old stars die

Collapse implode, explode....Nova events.

As much has been written and many studies done and published... I hope you now understand the question better.