Merging Star Systems

[mjryan44]

I am a novice and have a curious question.  if a star system, let's say a brown dwarf with its own planets, were to merge with ours, what would likely happen (please be specific)?  I assume such an event would produce quite severe and rather chaotic changes/disruptions.  Thanks.

[alanjgreen]

The effect of a star passing near the Oort Cloud would not have a good outcome for the solar system, the trillions of objects out there would be disrupted (pushed, pulled) by the new stars gravity, sending them randomly into new orbits, they would collide with each other adding more randomness. And many many of them would become attracted to the sun and head off into the inner solar system. It could take thousands of years for them to arrive. It would be a period of "heavy bombardment" all over again. It was this period that gave the moon its cratered appearance in the early solar system. The earth would have looked worse but active geology erased all the damage over time.

if a star were to pass into the inner solar system it would be a catastrophic life ending event. The planets would likely be eaten by the star or throw out into interstellar space. A new solar system would emerge over billions of years and be nothing like what we have now.

if the star actually merged with the sun, the destructive power of the event would destroy most of the solar system and negatively effect the solar systems in our locality too.

 

[alanjgreen]

The fact I like is the one where the Milky Way (400 billion stars) merges with Andromeda (one trillion stars) which is due to happen in 4billion years (I seem to remember) and no two stars will come together. The stars are just too far apart.

i take some comfort from this and it adds weight to the probability of your scenario being very low indeed  

[ronin]

I suspect that LIGO has called the idea that the chance of 2 stars merging is as close to zero as it is possible to get into question. Especially as the intention is to make LIGO better to detect more and less massive mergers. They must be expecting more events like that. It has not really been on line long and has recorded 2 and there is a third that is suspected of being a neutron star+black hole merger. Not heard a great deal of the present state of LIGO recently.

Additionally at 2 talks (Uni of Hertfordshire) it has been said that O and B type giants are formed by the merging of 2 (maybe more) stars in the cluster from which they came.

Bit odd to say but how many illistrations have we seen of two close stars with one taking the matter from the other - this being done to illiistrate a situation that is said to be occuring. That is to stars merging. Type 1a supernovas are said the be a white dwarf star accreting matter from a nearby companion star. That is merging with the proviso that before they merge into one the white dwarf will make a bit of a bang.

[coatesg]

On 08/02/2017 at 10:03, ronin said:

Additionally at 2 talks (Uni of Hertfordshire) it has been said that O and B type giants are formed by the merging of 2 (maybe more) stars in the cluster from which they came.

Yes - the merger of two stars is thought to be the source of blue stragglers in globular clusters. The chance of a head on collision is small, but the possibility of merger via tidal capture is far more likely. Here the outcome of the merger is a star that is much blue and hotter than would be expected for a star of its age in that cluster.

 

If there were orbiting planets, then one possible result for them would be expulsion from the system - 3 body systems are unstable, the two massive primary members not helping in the stability!

[Paul M]

I suppose one possibility is that in the right circumstances the Brown Dwarf would attempt to take up orbit around a common centre of gravity with the Sun. That barycenter might still be close to the Sun but not within it. 

Without considering any other planets, Jupiter's orbit would be totally disrupted and most likely it would be ejected or sent on a collision course. Add the other planets would result in chaos I suspect.

So that's my forecast. A chaotic system soon devoid of planets.

You'll notice I'm a bit lite on calculations here