Solar System Collisions

[Brian G Turner]

The revelation that other stars and their planets, and wandering exoplanets, could potentially infringe on our solar system and significantly affect it, came to me back in 1996.

However, looks like science has caught up, as reports detail a red dwarf and brown dwarf binary passed through the Oort Cloud 90,000 years ago - and that similar events may be more common than expected:
http://www.bbc.co.uk/news/science-environment-31519875

 

[Venusian Broon]

Seems like though it barely did anything though - if this had been a 'Hollywood scenario' it would have caused vast storms of comets bombarding the inner planets.

I suppose (although I haven't done the modelling) is that basically virtually all of the oort cloud objects that were moved by this fly-by where essentially thrown clean out of our system never to return. Comes back to the point that space is really big - I mean really, really big - so the chances of such oort objects been thrown in our direction by a random encounter were minuscule (?)

 

[Ray McCarthy]

It would have too far away to see, even if it had massive flares. A dim star a 1000x further away than Neptune / Kuiper belt.

It might have affected something, but it would take a very long time for any affected object to reach us.

Interesting though.

 

[Venusian Broon]

Just to show how fragile the orbits of anything coming in from very far - Comet Hyajutake that passed by us in 1996 (actually I think it gave a very good comet show, I remember seeing it low on the horizon) originally was thought to originally have a orbital period of 17,000 years - but because of gravitational nudges by the gas giants it now apparently has a period of 70,000 years!

@Ray McCarthy will give all those 'Ancient astronaut' theories a new lick of paint I'm sure - as I'm sure there will be those that claim that 'the inhabitants' of that fast moving star system hopped across when they were close

 

[Ray McCarthy]

I read Erik Von Danken when I was very young and naive. The Dan Brown of the 1970s?
I'd get an ulcer if I re-read Chariot of the Gods.

 

[BAYLOR]

If one of these wanders came into out solar system, wouldn't it simply be captured by suns gravity and brought into orbit somewhere in the solar system ?

 

[Venusian Broon]

If one of these wanders came into out solar system, wouldn't it simply be captured by suns gravity and brought into orbit somewhere in the solar system ?

If it travelled ~20 light years in 70,000 years then it was moving far too fast to be captured by the sun's gravity - that's approximately 85 km/sec.

The escape velocity of an object to leave the sun's gravitational pull at the relatively close orbit of, say, Neptune is only 7.7 km/sec - so these objects at closest approach 0.8 ly are way too fast!

 

[Dennis E. Taylor]

If one of these wanders came into out solar system, wouldn't it simply be captured by suns gravity and brought into orbit somewhere in the solar system ?

In a two-body problem, it's almost impossible to capture something. A body coming in from infinity is on a parabolic or hyperbolic orbit, which is open-ended. In order to turn it into an ellipse, the infalling body needs to lose some velocity. That's usually achieved by transferring it to a third body.

You do that in reverse when sending a probe out to the stars. The various slingshot maneuvers around planets like Jupiter transfer some of Jupiter's velocity to the probe.

 

[J Riff]

The galaxy is a gravitational well with power beyond our ability to calculate. I don't reckon there's anything wandering outside it's orbit around the centre, for zillions of years now. Must be giant, disguised, alien craft.

 

[Brian G Turner]

If one of these wanders came into out solar system, wouldn't it simply be captured by suns gravity and brought into orbit somewhere in the solar system ?

Depends on how fast the body was travelling, and presumably, the angle and direction of entry.

Space is apparently full of wandering planets - formed in other star systems, then ejected out. Some of these could theoretically enter our solar system, and some may already have - Uranus is a gas giant that has been knocked off its axis by a large body of some kind.

Additionally, while our solar system orbits the galactic centre of the Milky Way, not all star systems travel at the same orbital velocity. IMO it's entirely reasonable to presume sometimes our solar system and another might pass very close by indeed. Certainly earth has experienced a number of mass extinction events that IMO cannot simply be explained by atmospheric changes of meteor/comet strikes:

 

[Stephen Palmer]

There is a theory that the regularity of those mass extinction events is related to periodicity in how the Sun passes through sections of the galaxy. All fascinating stuff!

 

[steelyglint]

There are also gamma ray bursters. Fortunately the vast majority are in somebody else's back yard, but there must have been the odd one in the Milky Way over hundreds of millions of years. Something like that could easily depopulate half the globe.

A supernova close enough by could do major damage, too.

Basically, we live in a huge fireworks factory, and every so often some fool throws in a lighted match.

.

 

[Ursa major]

Regarding any adverse effects on Earth.... The Wiki article about this binary star states:

Comets perturbed from the Oort cloud would require roughly 2 million years to get to the inner Solar System.