<p>There are currently 3424 planets identified (including those in the Solar System and unconfirmed exoplanets). Of these, 3310 are confirmed exoplanets.</p>

<p>Out of the 3424, 180 are in binary (or multiple) star systems. Of those, 28 are circumbinary. I am not certain if any circumternary planets have been identified, though I know some circumternary disks have.</p>

<p>It is more difficult to identify circum-<em>n</em>-ary planets than those that only revolve around one star, so these numbers might not precisely represent the actual proportions.</p>

<p><strong>Source:</strong></p>

<ul>
<li><a href="http://www.openexoplanetcatalogue.com/" rel="nofollow">Open Exoplanet Catalogue</a></li>
</ul>

CC BY-SA 3.0
2016-07-13T16:32:15.503Z
this answer is absolutely amazing, thanks.  my grasp of the outline of the galaxy has been increased spectacularly.  I wish I could send over money  :)
Fattie
CC BY-SA 3.0
2016-07-13T16:33:34.157Z
@JoeBlow No need for compensation, a better answer would give you some theory about the likelihood of formation of circum-n-ary planets. Mine is just counting rows from a spreadsheet.
called2voyage
CC BY-SA 3.0
2016-07-13T17:44:42.677Z
just for the sake of being anal.  3310 confirmed.  regarding the 180 and 28 figures: are those two numbers "confirmed" category or "identified" category? thanks!
Fattie
CC BY-SA 3.0
2016-07-13T17:45:45.223Z
@JoeBlow As I specified, those are from the 3424 which includes confirmed and unconfirmed. Unfortunately, the list I was looking at didn't have a column indicating which were confirmed.
called2voyage
CC BY-SA 3.0
2016-07-14T00:36:16.453Z
exoplanets.org is more authoritative and discriminating in my view.
ProfRob
CC BY-SA 3.0
2016-07-14T00:37:02.823Z
@called2voyage of the 3424, what does it score as "planets" in our solar system?  I want to deduct those.
Fattie
CC BY-SA 3.0
2016-07-14T00:40:26.677Z
hooray! you can choose "Binary flag" on http://exoplanets.org/table
Fattie
CC BY-SA 3.0
2016-07-13T15:29:07.537Z
2016-07-13T15:29:07.537Z
called2voyage
<p>Since about 1990 astronomers been able to detect planets around other stars, using a couple different techniques, which is amazing.</p>

<p>By this point, do we know whether planets form <strong>only around single systems, only around multiple systems, or both</strong>??</p>

<p>(Surprisingly you can't find this general issue explained in popular writing. I think it's "obvious background knowledge" to experts, hence just doesn't get outlined explicitly in popular writing.)</p>

<p>So, as of mid 2016:</p>

<p>(i) About how many exoplanets do we know of (say, with good certainty),</p>

<p>(ii) In fact, how many (if any) of these are around single-star systems?</p>

<p>(iii) How many (if any) are around multiple-star systems?</p>

<p>If indeed it is possible to have planets in multiple systems: is it just a planet going around one of the stars, or is "all the way around both" known?</p>

CC BY-SA 3.0
2016-07-13T05:54:14.880Z
There appears to be minimal prior research going on here. There are many planets known in multiple star systems - of both types (circumbinary and orbiting one star).
ProfRob
CC BY-SA 3.0
2016-07-13T12:52:37.303Z
Two more examples on arXiv just this morning, https://arxiv.org/abs/1607.03038   https://arxiv.org/abs/1607.02525
ProfRob
CC BY-SA 3.0
2016-07-13T12:55:36.303Z
@Lelouch Circumbinary planets have to be at least ~5 times further way than the binary separation. There also appears to be a lack of planets around binaries with periods <7 days. This adds up to circumbinary planets must have periods >35 days. These are harder to find both in transit and doppler surveys.
ProfRob
CC BY-SA 3.0
2016-07-13T14:34:11.353Z
@JoeBlow Actually, I was wrong. The second paper seems to detail the planet I linked to. The first is actually new, and it is not clear from the abstract whether a planet has been spotted yet.
called2voyage
CC BY-SA 3.0
2016-07-13T14:34:44.930Z
@RobJeffries Are those papers actually about circumbinary/circumternary planets or just disks?
called2voyage
CC BY-SA 3.0
2016-07-13T15:04:19.737Z
Comments are not for extended discussion; this conversation has been [moved to chat](http://chat.stackexchange.com/rooms/42433/discussion-on-question-by-joe-blow-do-planets-form-around-lone-stars-multiple-s).
called2voyage
CC BY-SA 3.0
2016-07-13T15:44:53.410Z
@RobJeffries "There appears to be minimal prior research going on here." I don't think many lay-people know about arXiv, or how to search it. Given that as a undergraduate physicist I didn't have a working knowledge of finding cutting edge research until my 3rd or 4th year, I think we shouldn't expect that from most posters, so your comment sounds a bit mean.
FJC
CC BY-SA 3.0
2016-07-13T16:22:06.773Z
@FJC I don't think Rob meant that he expected users to search arXiv. If you google "circumbinary planets" a list comes up immediately. I think that is what Rob was talking about. The OP earlier stated that he was already familiar with the term "circumbinary planet", but in his post he is wondering if any have even been discovered. Rob, I think, is wondering why the OP didn't check google first, or if he did why he didn't include an explanation of why the search results were unsatisfactory.
called2voyage
CC BY-SA 3.0
2016-07-13T17:40:39.130Z
Unfortunately, the ones after I moved the conversation to chat cannot be moved to chat. The ones from before I'm leaving up so that Rob sees them. I can clean up the thread later.
called2voyage
CC BY-SA 3.0
2016-07-14T00:33:28.330Z
@FJC exoplanets.org. No need for arXIv it's all been done for you.
ProfRob
CC BY-SA 3.0
2016-09-25T01:58:56.657Z
I know recently they found several planets in at least 2 binary systems. Although I forget their designations. I think one of the planets was in the habitable zone of the Alpha star and was a super Earth with a 1.5 Earth Diameter.
JMC
<exoplanet><binary-star>
Do planets form around lone stars, multiple stars, or both? Do we know this yet?
Fattie
# Do planets form around lone stars, multiple stars, or both? Do we know this yet?

(Asked by: username_0 on 2016-07-12)

Since about 1990 astronomers been able to detect planets around other stars, using a couple different techniques, which is amazing.

By this point, do we know whether planets form **only around single systems, only around multiple systems, or both**??

(Surprisingly you can't find this general issue explained in popular writing. I think it's "obvious background knowledge" to experts, hence just doesn't get outlined explicitly in popular writing.)

So, as of mid 2016:

(i) About how many exoplanets do we know of (say, with good certainty),

(ii) In fact, how many (if any) of these are around single-star systems?

(iii) How many (if any) are around multiple-star systems?

If indeed it is possible to have planets in multiple systems: is it just a planet going around one of the stars, or is "all the way around both" known?

**Tags:** exoplanet, binary-star
> **Comments:**
> **username_1**: There appears to be minimal prior research going on here. There are many planets known in multiple star systems - of both types (circumbinary and orbiting one star).  
> **username_1**: Two more examples on arXiv just this morning, https://arxiv.org/abs/1607.03038   https://arxiv.org/abs/1607.02525  
> **username_1**: @Lelouch Circumbinary planets have to be at least ~5 times further way than the binary separation. There also appears to be a lack of planets around binaries with periods <7 days. This adds up to circumbinary planets must have periods >35 days. These are harder to find both in transit and doppler surveys.  
> **username_2**: @JoeBlow Actually, I was wrong. The second paper seems to detail the planet I linked to. The first is actually new, and it is not clear from the abstract whether a planet has been spotted yet.  
> **username_2**: @RobJeffries Are those papers actually about circumbinary/circumternary planets or just disks?  
> **username_2**: Comments are not for extended discussion; this conversation has been [moved to chat](http://chat.stackexchange.com/rooms/42433/discussion-on-question-by-joe-blow-do-planets-form-around-lone-stars-multiple-s).  
> **username_3**: @RobJeffries "There appears to be minimal prior research going on here." I don't think many lay-people know about arXiv, or how to search it. Given that as a undergraduate physicist I didn't have a working knowledge of finding cutting edge research until my 3rd or 4th year, I think we shouldn't expect that from most posters, so your comment sounds a bit mean.  
> **username_2**: @FJC I don't think Rob meant that he expected users to search arXiv. If you google "circumbinary planets" a list comes up immediately. I think that is what Rob was talking about. The OP earlier stated that he was already familiar with the term "circumbinary planet", but in his post he is wondering if any have even been discovered. Rob, I think, is wondering why the OP didn't check google first, or if he did why he didn't include an explanation of why the search results were unsatisfactory.  
> **username_2**: Unfortunately, the ones after I moved the conversation to chat cannot be moved to chat. The ones from before I'm leaving up so that Rob sees them. I can clean up the thread later.  
> **username_1**: @FJC exoplanets.org. No need for arXIv it's all been done for you.  
> **username_4**: I know recently they found several planets in at least 2 binary systems. Although I forget their designations. I think one of the planets was in the habitable zone of the Alpha star and was a super Earth with a 1.5 Earth Diameter.  

---

## 1 answers

### Answer by username_2 on 2016-07-13. Score: 3 | Accepted answer

There are currently 3424 planets identified (including those in the Solar System and unconfirmed exoplanets). Of these, 3310 are confirmed exoplanets.

Out of the 3424, 180 are in binary (or multiple) star systems. Of those, 28 are circumbinary. I am not certain if any circumternary planets have been identified, though I know some circumternary disks have.

It is more difficult to identify circum-*n*-ary planets than those that only revolve around one star, so these numbers might not precisely represent the actual proportions.

**Source:**

* [Open Exoplanet Catalogue](http://www.openexoplanetcatalogue.com/)

> **Comments:**
> **username_0**: this answer is absolutely amazing, thanks.  my grasp of the outline of the galaxy has been increased spectacularly.  I wish I could send over money  :)  
> **username_2**: @JoeBlow No need for compensation, a better answer would give you some theory about the likelihood of formation of circum-n-ary planets. Mine is just counting rows from a spreadsheet.  
> **username_0**: just for the sake of being anal.  3310 confirmed.  regarding the 180 and 28 figures: are those two numbers "confirmed" category or "identified" category? thanks!  
> **username_2**: @JoeBlow As I specified, those are from the 3424 which includes confirmed and unconfirmed. Unfortunately, the list I was looking at didn't have a column indicating which were confirmed.  
> **username_1**: exoplanets.org is more authoritative and discriminating in my view.  
> **username_0**: @called2voyage of the 3424, what does it score as "planets" in our solar system?  I want to deduct those.  
> **username_0**: hooray! you can choose "Binary flag" on http://exoplanets.org/table  

---

