Godfrey, Atlanta asked:
I had a question about what would happen if our solar system was in intergalactic space. For example instead of being in the Milky Way galaxy, it would be out there by itself in some place the BoŲtes void. I wanted to know would life still had been able to evolve? Would being a part of galaxy provide some sort of protection ?
Dave - I think if you managed to pick up our solar system and somehow magically transport to the middle of intergalactic space. There might be slightly high levels of really high energy intergalactic cosmic rays because the galaxy does have a magnetic field which will shield us from very high energy cosmic rays slightly. Again, a lot of cosmic rays are being made inside our galaxy so it probably cancels out a bit. I think the real thing is that you canít really get the solar system out into the middle of a big void like that. It doesnít get formed there because you need enough gas to form stars and thereís just nothing out there. So the only way you could get a star out there that would really something quite violent happening so youíd need to have three stars coming very close to each other and the other two dumping most of their energy into the third one and shooting it out into the galaxy or something.
Chris - There is an errant star, which is currently on its way out of the milkyway. I think itís even left the Milky Way. Itís destined to in the next, I think literally in hundreds of thousands or few thousand years. Itís actually gonna completely leave the galaxy and it was exactly as you said it was part of a binary system where the two were twirling around each other near to the central black hole. Theyíve got very, very rapidly accelerated and it was as of a sling shot where one spun away and the other one got trapped into potentially a trajectory to intergalactic space.
Dave - Yeah, and if itís done that, you know rip off, you know a planet is gonna be ripped off and held somewhere entirely different. It might also end up in intergalactic space but probably nowhere near the original star.
Chris - So, life as we knew it on those sorts of planets, that would be curtains, wouldnít it?
Dave - And also, you couldnít form a star which could support life as we know it outside of the galaxy because we depend on heavy elements, a lot heavier than iron. These were formed in the supernovae we weíre talking about earlier so you then get to the hydrogen helium and you canít really make a planet out of hydrogen helium and a little bit of lithium. So, although I think you could probably sustain it life out there, I canít see in any way of achieving it.
Godfrey asked the Naked Scientists: First, great show. I listen to it often, especially when I am working out at the gym. Also, what happens when a star with planets disintegrates? Do the planets just go off until capture by another star or they are ejected from the galaxy? If they are ejected from the galaxy, what happens to such planets? Godfrey Atlanta, Georgia, USA What do you think? Godfrey , Fri, 12th Jun 2009
My guess is that near planets would be vaporized. Their remnants would probably be in the shock-wave nebula; but I am not an expert; just guessing. Vern, Fri, 12th Jun 2009
When Andromeda collides with the Milky Way Galaxy sometime in the next four billion years, there is a 50% chance our solar system will be ejected from the newformed Milk-dromeda Galaxy (ref:Wikipedia, Milky Way-Andromeda Collision) Guest, Sun, 9th Feb 2014