<p>Oumuamua as an object is remarkable, because it has a positive net energy, which means it is not bound to the gravitational well of our sun. Therefore it will never return.</p>

CC BY-SA 4.0
2019-03-18T07:28:25.503Z
I'm not sure that really follows Q.E.D-like, so I've just asked [What natural mechanisms could lead to the unlikely case of the same rogue asteroid or planet passing through our solar system twice?](https://astronomy.stackexchange.com/q/30032/7982)
uhoh
CC BY-SA 4.0
2019-03-18T08:22:35.137Z
@uhoh: Well, it does. non-bound orbits have no solutions for return times. Of course you're free to envision a unlikely multiple scattering process that would make the object return, but that's at least a three-body system then, and my statement was about the two-body system of sun and test mass.
AtmosphericPrisonEscape
CC BY-SA 4.0
2019-03-18T08:26:11.340Z
That's like saying 2+3=11, then later saying "...and my statement was about base four arithmetic" ;-) Space has lots of bodies, and rogue asteroids exist only because of multi-body effects to begin with.
uhoh
CC BY-SA 4.0
2019-03-18T08:42:23.267Z
@uhoh: The main bodies that affect interstellar bodies are those with significant gravity wells, namely stars. So what you just said is irrelevant.
AtmosphericPrisonEscape
CC BY-SA 4.0
2019-03-18T08:49:58.863Z
I've written the linked question to explore a number of ways that "never" falls short and to provide the necessary space and venue to do so.
uhoh
CC BY-SA 4.0
2019-03-18T12:07:44.370Z
@AtmosphericPrisonEscape the question pretty much states your answer as a premise and specifically rules out the two-body scenario, asking only about interaction with other bodies.
Robert Frost
CC BY-SA 4.0
2019-03-17T21:23:36.547Z
2019-03-17T21:23:36.547Z
AtmosphericPrisonEscape
<p>Oumuamua is apparently a cigar-shaped asteroid that recently passed through the solar system on an unusual orbit, exhibiting unexpected acceleration.</p>

<p>Oumuamua is known to have fairly minimal powers of thrust other than gravitational free fall, insufficient in themselves to quickly turn around and accelerate the body, but they could be sufficient to enable it to influence itself to harness the gravitational effects of surrounding planetary bodies.  Assuming favourable thrust conditions, what is the soonest we could expect it to return?</p>

<p>*The <a href="https://www.nature.com/articles/s41586-018-0254-4" rel="nofollow noreferrer">extragravitational thrust</a> is of unknown cause.  The most popular explanation is that Oumuamua has some cometary properties and that it is caused by cometary outgassing in proximity to the Sun, although no cometary tail is apparent.</p>

CC BY-SA 4.0
2019-03-18T11:07:16.227Z
@user334732 - no, you have definitely not fixed the question. You wrote "is known to have fairly minimal powers of thrust" - no it doesn't. It is a rock. My vote is still very much a keep closed as entirely off topic.
Rory Alsop
CC BY-SA 4.0
2019-03-18T12:04:36.807Z
@RoryAlsop sorry, I thought this fact was so well known as to be taken for granted.  I've added a reference - is that better now?
Robert Frost
CC BY-SA 4.0
2019-03-18T12:25:27.637Z
The outgassing is very well known. And it's incredibly small. It's a rock.
Rory Alsop
CC BY-SA 4.0
2019-03-18T12:54:38.910Z
@RoryAlsop ah ok I get you know. You're saying the outgassing is only sufficient to generate fairly minimal thrust.
Robert Frost
CC BY-SA 4.0
2019-03-18T13:02:05.987Z
and classing it as thrust is misguided. Outgassing is incredibly small, and it really only happened at pretty close approach to the sun. There is not going to be measurable thrust once Oumuamua is away.
Rory Alsop
CC BY-SA 4.0
2019-03-18T14:20:32.733Z
@RoryAlsop I disagree about the classification as thrust.  And again, you're making assumptions. In fact this paper https://arxiv.org/abs/1809.06389v2 finds that Oumuama's tumbling is inconsistent with outgassing as a hypothesis for the observed extragravitational thrust.
Robert Frost
CC BY-SA 4.0
2019-03-18T14:48:54.840Z
Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/91210/discussion-between-rory-alsop-and-user334732).
Rory Alsop
<asteroids><navigation><oumuamua>
What's the soonest Oumuamua could return?
Robert Frost
# What's the soonest Oumuamua could return?

(Asked by: username_0 on 2019-03-17)

Oumuamua is apparently a cigar-shaped asteroid that recently passed through the solar system on an unusual orbit, exhibiting unexpected acceleration.

Oumuamua is known to have fairly minimal powers of thrust other than gravitational free fall, insufficient in themselves to quickly turn around and accelerate the body, but they could be sufficient to enable it to influence itself to harness the gravitational effects of surrounding planetary bodies. Assuming favourable thrust conditions, what is the soonest we could expect it to return?

\*The [extragravitational thrust](https://www.nature.com/articles/s41586-018-0254-4) is of unknown cause. The most popular explanation is that Oumuamua has some cometary properties and that it is caused by cometary outgassing in proximity to the Sun, although no cometary tail is apparent.

**Tags:** asteroids, navigation, oumuamua

> **Comments:**
> **username_1**: @user334732 - no, you have definitely not fixed the question. You wrote "is known to have fairly minimal powers of thrust" - no it doesn't. It is a rock. My vote is still very much a keep closed as entirely off topic.  
> **username_0**: @RoryAlsop sorry, I thought this fact was so well known as to be taken for granted.  I've added a reference - is that better now?  
> **username_1**: The outgassing is very well known. And it's incredibly small. It's a rock.  
> **username_0**: @RoryAlsop ah ok I get you know. You're saying the outgassing is only sufficient to generate fairly minimal thrust.  
> **username_1**: and classing it as thrust is misguided. Outgassing is incredibly small, and it really only happened at pretty close approach to the sun. There is not going to be measurable thrust once Oumuamua is away.  
> **username_0**: @RoryAlsop I disagree about the classification as thrust.  And again, you're making assumptions. In fact this paper https://arxiv.org/abs/1809.06389v2 finds that Oumuama's tumbling is inconsistent with outgassing as a hypothesis for the observed extragravitational thrust.  
> **username_1**: Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/91210/discussion-between-rory-alsop-and-user334732).  

---

## 1 answers

### Answer by username_2 on 2019-03-17. Score: 3

Oumuamua as an object is remarkable, because it has a positive net energy, which means it is not bound to the gravitational well of our sun. Therefore it will never return.

> **Comments:**
> **username_3**: I'm not sure that really follows Q.E.D-like, so I've just asked [What natural mechanisms could lead to the unlikely case of the same rogue asteroid or planet passing through our solar system twice?](https://astronomy.stackexchange.com/q/30032/7982)  
> **username_2**: @username_3: Well, it does. non-bound orbits have no solutions for return times. Of course you're free to envision a unlikely multiple scattering process that would make the object return, but that's at least a three-body system then, and my statement was about the two-body system of sun and test mass.  
> **username_3**: That's like saying 2+3=11, then later saying "...and my statement was about base four arithmetic" ;-) Space has lots of bodies, and rogue asteroids exist only because of multi-body effects to begin with.  
> **username_2**: @username_3: The main bodies that affect interstellar bodies are those with significant gravity wells, namely stars. So what you just said is irrelevant.  
> **username_3**: I've written the linked question to explore a number of ways that "never" falls short and to provide the necessary space and venue to do so.  
> **username_0**: @username_2 the question pretty much states your answer as a premise and specifically rules out the two-body scenario, asking only about interaction with other bodies.  

---

