I was reading about the impending collision of our galaxy with the Andromeda galaxy, and learned that there is a small possibility that our solar system could be ejected during the collision.

Assuming that orbits within our solar system remain unchanged (it is ejected as a whole), would floating in intergalactic space cause any significant changes in the living conditions on earth?

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    $\begingroup$ There's actually a very good answer to this on the physics forum physics.stackexchange.com/questions/112887/…, it covers lots of angles including the pros and cons of leaving the galaxy. $\endgroup$
    – Dean
    Mar 23, 2016 at 20:00
  • $\begingroup$ Oort cloud included, or not? $\endgroup$ Mar 24, 2016 at 16:34
  • $\begingroup$ I assume that if the oort cloud was disturbed that would mean a significant increase in the chances of cataclysmic impact, but I think that the oort cloud would be considered a set of "orbits within our solar system", since its objects orbit our sun- right? $\endgroup$
    – Andrew
    Mar 24, 2016 at 17:02
  • $\begingroup$ @Andrew Right, but if the disturbing star comes in from, say, the left side, then Oort objects on the right side aren't going to be nearly so disturbed. Depending on geometry, we could totally lose some of the outer planets as well. $\endgroup$ Mar 24, 2016 at 19:59
  • $\begingroup$ If your question is a thought experiment where you take the solar system as it is today and "beam it" unaltered (Oort cloud and all) to a location well outside the Milky Way, then I think it would be better (lower density of radiation and less chance of an object perturbing the Oort cloud and hurling something our way). It would be sad not to have a sky full of stars, with the dream of traveling to one, but the Milky Way would be a sight to behold. Of course, the Earth will be uninhabitable long before the Milky Way and Andromeda collide. $\endgroup$ Mar 25, 2016 at 1:05

2 Answers 2


The Solar System moving through intergalactic space would have no impact on life. However, in order for the sun to be ejected out of the Galaxy, a very close encounter with a stellar mass object would be necessary. That would likely have a huge negative impact on life on earth, at a minimum perturbing many objects in the Oort Cloud into the inner solar syste. At the other end of the spectrum, the orbit of earth could be significantly altered or the earth could even be ejected from the solar system, depending on the geometry of the encounter.

  • $\begingroup$ A simple collision with another star cannot impart additional kinetic energy to the Sun. $\endgroup$
    – ProfRob
    Apr 10, 2016 at 10:12
  • $\begingroup$ A stellar collision is not what I was referring to. $\endgroup$
    – Dave
    Apr 10, 2016 at 16:29
  • $\begingroup$ Substitute the words "close encounter with a stellar mass object". There would have to be a third body involved - i.e. an interaction with a close binary. I do not think this is the way that stars are ejected in a galaxy collision. $\endgroup$
    – ProfRob
    Apr 10, 2016 at 16:38

I can think of two ways this benefits life.

  • Less chance of a passing star disrupting our Oort Cloud and sending deadly comets crashing into the Earth.
  • Less chance of nearby supernova destroying our ozone layer.

On the other hand, if our Solar System passes near a relativistic jet emanating from the central black hole of a galaxy, Earth will get hit with high speed particles that will disrupt the magnetosphere and ozone layer. Definitely not good for any life on Earth at that time.

Getting ejected from the galaxy also means there is less chance of future humans exploring the galaxy by hopping to nearby stars. We'd only have our solar system to explore and colonize. There would not be another star system within a hundred thousand light years.


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