<p>It would be more accurate to call them surveys than studies.   A study looks at an object in detail.  A survey counts and categorizes objects.</p>

<p>Rogue planets are enormously difficult to see, and only a few very large ones have actually been observed directly.  For the largest rogue planets, it's unclear if they actually are ejected planets as opposed to failed stars. </p>

<p><a href="https://www.scientificamerican.com/article/wandering-in-the-void-billions-of-rogue-planets-without-a-home/" rel="nofollow noreferrer">This article discusses rogue planets</a> in pretty good detail.  </p>

<p>In 2011 <a href="https://www.nature.com/articles/nature10092.epdf?referrer_access_token=geHqH2LOeheWU0uQ5zmABtRgN0jAjWel9jnR3ZoTv0Nk9JKZpv6lE-Lv9RamE8LN_ITJRcpMAMnSPNrwy6k6bSv1eIUy6t5iaklA6KT6lNrV3u7Tq63z5DJrzdRm91bMCy-ICeVl6b6pe4ra9NjfPrf8lsyw8lYocA5V-YsUN0gBrM2qGsMIMFEgS-aWJ5ZD&amp;tracking_referrer=www.scientificamerican.com" rel="nofollow noreferrer">the MOA survey</a> was published, estimating a high number of Jupiter sized Rogue planets, perhaps outnumbering stars. </p>

<p>More recently the <a href="https://en.wikipedia.org/wiki/Optical_Gravitational_Lensing_Experiment" rel="nofollow noreferrer">OGLE Project</a> estimated about 1/10th that many rogue Jupiters, which is more in line with statistical predictions.   Smaller planets are more likely to get ejected from their solar-systems than larger ones.    Rogue Juiters outnumbering stars seemed unlikely and my understanding is that most scientists are more in line with the OGLE estimate than MOA.</p>

<p>Both estimates rely on microlensing which amounts to very small and temporary changes when rogue planets drift between the Earth and a star.  There's a fairly large margin of error for both surveys.</p>

<p>NASA's <a href="https://wfirst.gsfc.nasa.gov/" rel="nofollow noreferrer">WFIRST telescope</a> should answer a lot of questions on rogue planets.   It's not expected to be launched till the mid 2020s though.</p>

CC BY-SA 3.0
2017-11-23T17:33:22.697Z
2017-11-24T06:53:10.420Z
2017-11-24T06:53:10.420Z
userLTK
<p>I am interested in studies and/or publications about planets that wander in space and are not orbiting around a star or its remnants. These dark and frozen worlds should've got ripped away from their respective system by a large passing body (another star? passing black hole) or any other astronomical event (which one?).</p>

<p>I am curious, whether there exist statistical estimates on the number of such planets and the rate at which they are produced. I am also interested in reading about the statistical models that can produce those estimates and encode researchers' beliefs. If there are no such models, why?</p>

<p>A provoking thought: According to Greek, such planets are really fitting their name πλάνητες ἀστέρες (planētes asteres, "wandering stars") or simply πλανῆται (planētai, "wanderers"). It is frightening to imagine such world that drifts deeper and deeper into empty space. Forever.</p>

CC BY-SA 3.0
2017-11-18T00:43:05.520Z
https://en.wikipedia.org/wiki/Rogue_planet
Cody
CC BY-SA 3.0
2017-11-18T03:26:35.177Z
Small point, but the majority of Rogue planets probably come from planetary migration not large bodies passing through - though I don't think anyone has solid numbers on that, planetary migration is likely the biggest source.
userLTK
CC BY-SA 3.0
2017-11-18T03:28:13.410Z
Also, some links to statistical studies in the answer here:   https://astronomy.stackexchange.com/questions/1564/motion-of-rogue-planets/23312#23312   Observation is very difficult and quite limited so far, so studies have a significant margin of error.
userLTK
CC BY-SA 3.0
2017-11-20T17:51:14.307Z
How exactly would you distinguish a formerly orbiting body from a random coalcescence of matter in deep space?
Carl Witthoft
<exoplanet><rogue-planet><resource-request>
Studies on planets without parent star
Vladislavs Dovgalecs
# Studies on planets without parent star

(Asked by: username_0 on 2017-11-17)

I am interested in studies and/or publications about planets that wander in space and are not orbiting around a star or its remnants. These dark and frozen worlds should've got ripped away from their respective system by a large passing body (another star? passing black hole) or any other astronomical event (which one?).

I am curious, whether there exist statistical estimates on the number of such planets and the rate at which they are produced. I am also interested in reading about the statistical models that can produce those estimates and encode researchers' beliefs. If there are no such models, why?

A provoking thought: According to Greek, such planets are really fitting their name πλάνητες ἀστέρες (planētes asteres, "wandering stars") or simply πλανῆται (planētai, "wanderers"). It is frightening to imagine such world that drifts deeper and deeper into empty space. Forever.

**Tags:** exoplanet, rogue-planet, resource-request

> **Comments:**
> **username_1**: https://en.wikipedia.org/wiki/Rogue_planet  
> **username_2**: Small point, but the majority of Rogue planets probably come from planetary migration not large bodies passing through - though I don't think anyone has solid numbers on that, planetary migration is likely the biggest source.  
> **username_2**: Also, some links to statistical studies in the answer here:   https://astronomy.stackexchange.com/questions/1564/motion-of-rogue-planets/23312#23312   Observation is very difficult and quite limited so far, so studies have a significant margin of error.  
> **username_3**: How exactly would you distinguish a formerly orbiting body from a random coalcescence of matter in deep space?  

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## 1 answers

### Answer by username_2 on 2017-11-23. Score: 6

It would be more accurate to call them surveys than studies. A study looks at an object in detail. A survey counts and categorizes objects.

Rogue planets are enormously difficult to see, and only a few very large ones have actually been observed directly. For the largest rogue planets, it's unclear if they actually are ejected planets as opposed to failed stars.

[This article discusses rogue planets](https://www.scientificamerican.com/article/wandering-in-the-void-billions-of-rogue-planets-without-a-home/) in pretty good detail.

In 2011 [the MOA survey](https://www.nature.com/articles/nature10092.epdf?referrer_access_token=geHqH2LOeheWU0uQ5zmABtRgN0jAjWel9jnR3ZoTv0Nk9JKZpv6lE-Lv9RamE8LN_ITJRcpMAMnSPNrwy6k6bSv1eIUy6t5iaklA6KT6lNrV3u7Tq63z5DJrzdRm91bMCy-ICeVl6b6pe4ra9NjfPrf8lsyw8lYocA5V-YsUN0gBrM2qGsMIMFEgS-aWJ5ZD&tracking_referrer=www.scientificamerican.com) was published, estimating a high number of Jupiter sized Rogue planets, perhaps outnumbering stars.

More recently the [OGLE Project](https://en.wikipedia.org/wiki/Optical_Gravitational_Lensing_Experiment) estimated about 1/10th that many rogue Jupiters, which is more in line with statistical predictions. Smaller planets are more likely to get ejected from their solar-systems than larger ones. Rogue Juiters outnumbering stars seemed unlikely and my understanding is that most scientists are more in line with the OGLE estimate than MOA.

Both estimates rely on microlensing which amounts to very small and temporary changes when rogue planets drift between the Earth and a star. There's a fairly large margin of error for both surveys.

NASA's [WFIRST telescope](https://wfirst.gsfc.nasa.gov/) should answer a lot of questions on rogue planets. It's not expected to be launched till the mid 2020s though.


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