<p>There's also the possibility that a rogue giant planet may have a moon with a subsurface ocean of liquid water due to tidal heating in an orbit close enough to its parent planet. E.g. if Jupiter was a rogue planet its moon Europa could still harbor life because of tidal heating.</p>
<blockquote>
<p>Around five percent of Earth-sized ejected planets with Moon-sized natural satellites would retain their satellites after ejection. A large satellite would be a source of significant geological tidal heating<sup>26</sup>.</p>
</blockquote>
<ul>
<li><a href="https://en.wikipedia.org/wiki/Rogue_planet#Sunless,_yet_warm" rel="noreferrer">Wikipedia</a></li>
</ul>
<p><Sub>26. Debes, John H.; Steinn Sigurðsson (20 October 2007). &quot;The Survival Rate of Ejected Terrestrial Planets with Moons&quot;. The Astrophysical Journal Letters. 668 (2): L167–L170. arXiv:0709.0945</sub></p>

CC BY-SA 4.0
2021-07-15T16:25:48.853Z
@Pureferret Why would you think rogue planets can't have satellites?
John
CC BY-SA 4.0
2021-07-15T18:26:26.133Z
I thought if a planet was knocked out of orbit, that the moon would be almost certainly knocked away? Is that wrong?
AncientSwordRage
CC BY-SA 4.0
2021-07-15T18:36:30.643Z
@Pureferret [From Wikipedia](https://en.wikipedia.org/wiki/Rogue_planet#Sunless,_yet_warm) *"Around five percent of Earth-sized ejected planets with Moon-sized natural satellites would retain their satellites after ejection. A large satellite would be a source of significant geological tidal heating.[26]"*
Aubreal
CC BY-SA 4.0
2021-07-15T20:57:27.503Z
A rogue planet could also pick up moons after being ejected.
Don Branson
CC BY-SA 4.0
2021-07-15T22:20:11.207Z
@Pureferret An ejected planet can retain its moon, see my answer here: https://astronomy.stackexchange.com/questions/41832/could-an-orphan-rogue-planet-have-a-moon/41838#41838
Connor Garcia
CC BY-SA 4.0
2021-07-15T05:47:51.133Z
2021-07-15T21:17:04.750Z
2021-07-15T21:17:04.750Z
John
<p>In short, if a rogue planet has enough internal heat and retains enough of that internal heat by a thick atmosphere or within a miles-deep ice crust, it could be warm enough for liquid water and thus possibly for Earth-like lifeforms.</p>
<p>here is a link to an article on the subject:</p>
<p><a href="https://futurism.com/life-could-exist-on-rogue-planets-that-dont-have-stars" rel="noreferrer">https://futurism.com/life-could-exist-on-rogue-planets-that-dont-have-stars</a></p>
<p>And an advanced civlization capable of building artifical habitats on lifeless worlds or in outer space could settle a rogue planet, providing their own energy source from nuclear fusion.</p>

CC BY-SA 4.0
2021-07-14T18:30:54.000Z
I think you need to trim the end of the link: https://futurism.com/life-could-exist-on-rogue-planets-that-dont-have-stars . Perhaps of interest to the OP, the popular science youtube channel Kurzgesagt had some videos on this topic: https://www.youtube.com/watch?v=gLZJlf5rHVs , https://www.youtube.com/watch?v=M7CkdB5z9PY
eps
CC BY-SA 4.0
2021-07-14T18:04:31.603Z
2021-07-15T17:37:16.117Z
2021-07-15T17:37:16.117Z
M. A. Golding
<p>The discussion will focus on</p>
<ul>
<li><p>the term <em>rogue planet</em> is an oxymoron, as it's missing the principle defining feature of a planet.</p>
</li>
<li><p>a Jupiter-sized body without a sun will be warmer than you would have thought.  And they could be even larger, up to being brown dwarfs.</p>
</li>
<li><p>moons of such a body can be heated by tidal forces, without regard to whether there's a sun or not.</p>
</li>
</ul>

CC BY-SA 4.0
2023-01-27T05:43:50.603Z
I would agree that *rogue planet* is a bad term. In my opinion, "rōnin planet" would be more adequate.
https://en.wikipedia.org/wiki/R%C5%8Dnin
Michael_1812
CC BY-SA 4.0
2021-07-15T23:18:41.270Z
2021-07-15T23:18:41.270Z
JDługosz
<p>On July 21 at 10 am, Seti Talks will be discussing the topic of &quot;Could Rogue Planets Harbor Life&quot;. Supposedly there are 50 billion such planets in the Milky Way. I would think that the answer was obvious: no. So what is there to discuss?</p>

CC BY-SA 4.0
2021-07-15T14:22:48.213Z
I wouldn't rule out life anywhere in the universe.
PeterH
CC BY-SA 4.0
2021-07-15T20:05:21.750Z
Life doesn't have to take a form in any way similar to what we've previously been exposed to in this world.  When we look at things like the need for water, carbon-based chemistry, etc., these types of natural characteristics are simply based on past experience, not proven laws of the universe.
Panzercrisis
CC BY-SA 4.0
2021-07-15T20:51:53.490Z
Somewhere on a rogue planet - "Could star-bound planets harbor life? Seems unlikely, all that radiation."
Don Branson
CC BY-SA 4.0
2021-07-16T09:07:28.827Z
Life, uh, finds a way.
AnoE
CC BY-SA 4.0
2021-07-16T23:05:12.730Z
@Panzercrisis: It's hard to imagine any form of life that doesn't require an external energy source though.
Mooing Duck
CC BY-SA 4.0
2021-07-17T03:35:09.927Z
Primitive life, probably yes. But no way are you evolving the complexity of, say a moth that has *two separate body plans* in it's lifecycle. There is simply way too little energy to get very far.
Kevin Kostlan
<exoplanet><life><rogue-planet>
Could rogue planets harbor life?
Peter U
# Could rogue planets harbor life?

(Asked by: username_0 on 2021-07-14)

On July 21 at 10 am, Seti Talks will be discussing the topic of "Could Rogue Planets Harbor Life". Supposedly there are 50 billion such planets in the Milky Way. I would think that the answer was obvious: no. So what is there to discuss?

**Tags:** exoplanet, life, rogue-planet

> **Comments:**
> **username_1**: I wouldn't rule out life anywhere in the universe.  
> **username_2**: Life doesn't have to take a form in any way similar to what we've previously been exposed to in this world.  When we look at things like the need for water, carbon-based chemistry, etc., these types of natural characteristics are simply based on past experience, not proven laws of the universe.  
> **username_3**: Somewhere on a rogue planet - "Could star-bound planets harbor life? Seems unlikely, all that radiation."  
> **username_4**: Life, uh, finds a way.  
> **username_5**: @username_2: It's hard to imagine any form of life that doesn't require an external energy source though.  
> **username_6**: Primitive life, probably yes. But no way are you evolving the complexity of, say a moth that has *two separate body plans* in it's lifecycle. There is simply way too little energy to get very far.  

---

## 3 answers

### Answer by username_7 on 2021-07-15. Score: 21

There's also the possibility that a rogue giant planet may have a moon with a subsurface ocean of liquid water due to tidal heating in an orbit close enough to its parent planet. E.g. if Jupiter was a rogue planet its moon Europa could still harbor life because of tidal heating.

> Around five percent of Earth-sized ejected planets with Moon-sized natural satellites would retain their satellites after ejection. A large satellite would be a source of significant geological tidal heating26.

* [Wikipedia](https://en.wikipedia.org/wiki/Rogue_planet#Sunless,_yet_warm)

26. Debes, username_7 H.; Steinn Sigurðsson (20 October 2007). "The Survival Rate of Ejected Terrestrial Planets with Moons". The Astrophysical Journal Letters. 668 (2): L167–L170. arXiv:0709.0945

> **Comments:**
> **username_7**: @Pureferret Why would you think rogue planets can't have satellites?  
> **username_8**: I thought if a planet was knocked out of orbit, that the moon would be almost certainly knocked away? Is that wrong?  
> **username_9**: @Pureferret [From Wikipedia](https://en.wikipedia.org/wiki/Rogue_planet#Sunless,_yet_warm) *"Around five percent of Earth-sized ejected planets with Moon-sized natural satellites would retain their satellites after ejection. A large satellite would be a source of significant geological tidal heating.[26]"*  
> **username_3**: A rogue planet could also pick up moons after being ejected.  
> **username_10**: @Pureferret An ejected planet can retain its moon, see my answer here: https://astronomy.stackexchange.com/questions/41832/could-an-orphan-rogue-planet-have-a-moon/41838#41838  

---

### Answer by username_11 on 2021-07-14. Score: 13

In short, if a rogue planet has enough internal heat and retains enough of that internal heat by a thick atmosphere or within a miles-deep ice crust, it could be warm enough for liquid water and thus possibly for Earth-like lifeforms.

here is a link to an article on the subject:

<https://futurism.com/life-could-exist-on-rogue-planets-that-dont-have-stars>

And an advanced civlization capable of building artifical habitats on lifeless worlds or in outer space could settle a rogue planet, providing their own energy source from nuclear fusion.

> **Comments:**
> **username_12**: I think you need to trim the end of the link: https://futurism.com/life-could-exist-on-rogue-planets-that-dont-have-stars . Perhaps of interest to the OP, the popular science youtube channel Kurzgesagt had some videos on this topic: https://www.youtube.com/watch?v=gLZJlf5rHVs , https://www.youtube.com/watch?v=M7CkdB5z9PY  

---

### Answer by username_13 on 2021-07-15. Score: 4

The discussion will focus on

* the term *rogue planet* is an oxymoron, as it's missing the principle defining feature of a planet.
* a Jupiter-sized body without a sun will be warmer than you would have thought. And they could be even larger, up to being brown dwarfs.
* moons of such a body can be heated by tidal forces, without regard to whether there's a sun or not.

> **Comments:**
> **username_14**: I would agree that *rogue planet* is a bad term. In my opinion, "rōnin planet" would be more adequate. https://en.wikipedia.org/wiki/R%C5%8Dnin  

---

