<p>While near encounters with supermassive black holes are bad for the stability of solar systems [citation needed?], many intergalactic stars become intergalactic without a close encounter. They are <a href="https://en.wikipedia.org/wiki/Galactic_tide" rel="noreferrer">part of streams and tidal tails that emerge when galaxies or globular clusters get tidally disrupted by another galaxy</a>. </p>

<p>Still, even <a href="https://arxiv.org/abs/1201.1446" rel="noreferrer">while encounters with black holes are usually disruptive simulations suggest that some planets may remain around the star</a>. This is most likely for planets real close to the star, like hot jupiters. </p>

CC BY-SA 3.0
2018-03-13T15:20:01.637Z
2018-03-13T15:20:01.637Z
Anders Sandberg
<p>Given that we've discovered hundreds of <a href="https://en.wikipedia.org/wiki/Intergalactic_star" rel="noreferrer">intergalactic stars</a> (IGs), and that most stars <a href="https://www.space.com/24894-exoplanets-habitable-zone-red-dwarfs.html" rel="noreferrer">have planets</a>, what do we know about the likelihood of IGs retaining their planets after being ejected from their galaxy?</p>

<p>Related to that, what are the chances of <a href="https://en.wikipedia.org/wiki/Rogue_planet" rel="noreferrer">rogue planets</a> being intergalactic as well? If there's a planet floating out in intergalactic space, is it more likely to be orbiting a star, or on it's own?</p>

CC BY-SA 3.0
2018-03-13T14:17:59.263Z
Why would you think otherwise?  "fling" is relative;  the gravitational force between star and planet is much greater than the external force which ejected the star +planet(s) from a galaxy.
Carl Witthoft
<star><planet><rogue-planet><intergalactic-space>
Is it likely that intergalactic stars would still retain their planets?
joseph.hainline
# Is it likely that intergalactic stars would still retain their planets?

(Asked by: username_0 on 2018-03-13)

Given that we've discovered hundreds of [intergalactic stars](https://en.wikipedia.org/wiki/Intergalactic_star) (IGs), and that most stars [have planets](https://www.space.com/24894-exoplanets-habitable-zone-red-dwarfs.html), what do we know about the likelihood of IGs retaining their planets after being ejected from their galaxy?

Related to that, what are the chances of [rogue planets](https://en.wikipedia.org/wiki/Rogue_planet) being intergalactic as well? If there's a planet floating out in intergalactic space, is it more likely to be orbiting a star, or on it's own?

**Tags:** star, planet, rogue-planet, intergalactic-space
> **Comments:**
> **username_1**: Why would you think otherwise?  "fling" is relative;  the gravitational force between star and planet is much greater than the external force which ejected the star +planet(s) from a galaxy.  

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## 1 answers

### Answer by username_2 on 2018-03-13. Score: 6

While near encounters with supermassive black holes are bad for the stability of solar systems [citation needed?], many intergalactic stars become intergalactic without a close encounter. They are [part of streams and tidal tails that emerge when galaxies or globular clusters get tidally disrupted by another galaxy](https://en.wikipedia.org/wiki/Galactic_tide).

Still, even [while encounters with black holes are usually disruptive simulations suggest that some planets may remain around the star](https://arxiv.org/abs/1201.1446). This is most likely for planets real close to the star, like hot jupiters.


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