I'm putting together a scenario, where a "Sun" and some debris are flung so distant that 14 billion years after the big bang, it has an "Earth" (and maybe some other minor rocky/icy objects), but no stars are observable to the naked eye.

I know we can't see anything other than our own galaxy with the naked eye, but this would be a galaxy-less "rogue" star. Is this possible - if so, how?


4 Answers 4


Galactic Collisions

This sort of stuff will happen a lot during galactic collisions. In the gravitational chaos, groups of stars, star-forming gas clouds, or even individual star systems can easily get ejected. Like in @HDE226868's answer, except in my scenario you could also expect the ejection of regular, sun-like stars with high enough metallicity to have rocky planets.

enter image description here

The long tails you see in the picture are streams of stars getting lost into the great intergalactic vacuum. If thrown out in the right direction, such a star could eventually get far away enough from other galaxies that no stars would be visible to a human-level eye.

If this sounds far fetched, think about the fact that our Galaxy and Andromeda are going to collide in a billion years or so.

  • 1
    $\begingroup$ Nice answer; I can't believe I didn't think of this. Also, cool pictures! $\endgroup$
    – HDE 226868
    Jan 28, 2016 at 21:34
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    $\begingroup$ Compare What would be the effects of galaxies colliding? $\endgroup$
    – user
    Jan 28, 2016 at 21:43
  • $\begingroup$ How long would it take for a star to get far enough? Would it be before the star burned out? $\endgroup$
    – svick
    Jan 28, 2016 at 23:29
  • $\begingroup$ For a very, very rough "or so". It's more like 4 billion years! $\endgroup$ Jan 29, 2016 at 1:46
  • $\begingroup$ @svick maybe our star is the one that formed formed from the stars that got thrown out. Or a generation later. $\endgroup$
    – Christian
    Apr 16, 2019 at 14:34

It's totally possible (sort of)!

Such stars are called - not surprisingly - intergalactic stars. These stars are often referred to as hypervelocity stars, because in order to reach galactic escape velocity, they have to be traveling really quickly.

The current theory is that a pair of binary stars encounters the supermassive black hole at the center of their galaxy. One star goes towards the central black hole, while the other is flung out of the galaxy at an enormous speed.

Image in the public domain.

This graphic details a three-star system encountering the supermassive black hole, but the same setup works just as well with only two stars. Only one will be ejected, not two.

That said, galaxies would still most likely be visible from a planet orbiting the star. Many galaxies can be seen with the naked eye, and this would still be the case for planets outside the galaxy. So it's likely that inhabitants of this planet (if there are any) would still see plenty of galaxies. They'd just be very, very faint, for the most part.

Additionally, we have to deal with the issue of the orbital stability of the material orbiting the planet. Any encounter strong enough to fling the star out of the galaxy might dislodge the debris from its orbit around the star, sending it somewhere completely different. I would think it unlikely for the star to pick up a substantial amount of planet-forming material on its way out, and certainly not outside the galaxy in the intergalactic medium, but its possible.

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    $\begingroup$ "Any encounter strong enough to fling the star out of the galaxy might dislodge the planet from its orbit" -- unless it picked up the material to form the planet (or just snagged the planet itself) on its way out of the galaxy. Besides, for the timeframe OP wants, the star had to have had that encounter a VERY long time ago anyway, so it's not like anyone alive today on that planet was alive to witness it, nor even part of any primordial soup at the time! $\endgroup$
    – Kromey
    Jan 28, 2016 at 21:37
  • $\begingroup$ @Kromey Thanks for the correction; I had missed that only debris was flung along with the star. $\endgroup$
    – HDE 226868
    Jan 28, 2016 at 21:39
  • $\begingroup$ The star could still pick up material on its way out, I don't think orbital stability is a matter of concern at all really: A star ejected from our own galaxy like this would have to cross ~90,000 light years before it left. At galactic escape velocity of ~537 km/s (space.stackexchange.com/a/3949), it would take the star ~1.6x10^12 years to escape the galaxy, and much longer before individual stars can no longer be seen -- more than ample time to accumulate matter and form entirely new planets, even starting from scratch! $\endgroup$
    – Kromey
    Jan 28, 2016 at 21:44
  • $\begingroup$ @Kromey I would argue that the tidal forces near the black hole would severely disrupt any matter in a debris/protoplanetary disk, and that the star would be traveling so fast that if it passed through any high-density region of space, it wouldn't have much time to pick up matter. It would simply move on without accreting a lot of material. Space is pretty empty, and there's not a lot to work off of, even in interstellar clouds. $\endgroup$
    – HDE 226868
    Jan 28, 2016 at 21:47
  • $\begingroup$ @Kromey - The closest individual stars which can be seen at present are probably no more than about 4000 ly away, as opposed to the diffuse Milky Way. The thickness of the Orion arm is esitimated at about 2000 ly, so an ejection perpendicular to the galactic plane would only need to travel ~ 5000 ly, ignoring other rogues. At your specified velocity it would take about 9 x 10^10 years. $\endgroup$ Feb 8, 2016 at 22:52

A bit late, but anyway...

Building on the comments to the question, since you talk about a rogue star (with a "earth") and objects visible to the naked eye, you have a "simple" option: just put your rogue star about 30/40 million light years away from the nearest object.

Or, for example, you can put it in the so called "supervoid", an existing empty area in space (1.8 billion light years across): this way your earth has about a billion light years in every direction without stars/galaxies, which should be enough to have a dark sky without observable objects, at least to the naked eye.

As you can read in this question on Astronomy at SE, it seems that the furthest object claimed to be visible with the naked eye is M83, at about 15 million light years.


It seems reasonable that any solar system that's wandering around without a galaxy would be in an area that is relatively dark, so the relatively-near galaxies would appear as stars do to us. It's likely that we can't see galaxies unaided because of all the "light pollution" provided by the Milky Way.


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