<p><a href="https://arxiv.org/abs/2002.12006" rel="nofollow noreferrer">A recent paper</a> suggests that there are possibly more planets around binary stars than we have been able to detect because of observational biases. This means that there are more planets in binary systems than what we have discovered. From <a href="http://exoplanet.eu/planets_binary/" rel="nofollow noreferrer">exoplanet.eu</a></p>

<blockquote>
  <p>until recently, observational surveys, especially those relying on the radial velocity method, had been strongly biased against binaries</p>
</blockquote>

<p>and </p>

<blockquote>
  <p>for many cases, the binarity of the system was not known at the time of the exoplanet's discovery and was established by later observational campaigns. This means that there should still be a potentially large population of exoplanet-hosting "single" stars that are in fact members of a (yet undetected) multiple system.</p>
</blockquote>

<p>However, the formation of planets is impeded, and any planets are more likely to be thrown out of the system when the separation between both stars is less than 100 AU. So the fraction of binary systems with planets should be smaller than the fraction of single stars with planets. </p>

<p>Another <a href="https://arxiv.org/abs/2002.11734" rel="nofollow noreferrer">recent paper</a> addresses the question of the frequency of planets in binary star systems based on data from Gaia's second release. Around close binaries, there are very few planets. However, there seem to be many planets around binaries with a white dwarf. So how many planets are around binary stars seems to depend on the geometry of the binary star system. </p>

<hr>

<p>On a side note, the "other kind" of planet in the xkcd strip is referred to as a "circumstellar planet". </p>

CC BY-SA 4.0
2020-02-28T13:08:09.117Z
2020-04-06T15:06:18.733Z
2020-04-06T15:06:18.733Z
usernumber
<p>Go to the exoplanets.org database.</p>

<p>Top left hand dropdown menu - select "Stars"</p>

<p>You get a table listing all the known stars with exoplanets.</p>

<p>Click on the big plus sign in the top right hand of the table and select "Binary Flag"</p>

<p>This will now show a boolean flag that indicates if the star is known to be part of a binary (or multiple) system.</p>

<p>In the FILTER window at the top of the page, just type "BINARY" and the table will just show binary stars.</p>

<p>It is possible to export the table as a csv file using the "export" button at the top right. Counting the number of lines with the BINARY flag indicates that as of December 2019, there are 511 known exoplanets around binary stars. </p>

CC BY-SA 4.0
2020-02-28T10:55:18.903Z
Does the database also indicate which planets are circumbinary and which planets are the other kind?
usernumber
CC BY-SA 4.0
2019-12-05T18:13:31.050Z
2020-01-30T17:42:56.127Z
2020-01-30T17:42:56.127Z
ProfRob
<p><a href="https://what-if.xkcd.com/150/" rel="nofollow noreferrer">This XKCD whatif</a> talks about circumbinary and [the other kind of] exoplanets. How many such exoplanets have actually been discovered?
<a href="https://i.sstatic.net/8x6ip.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/8x6ip.png" alt="enter image description here"></a></p>

<p>I tried to look it up at <a href="http://exoplanets.org/" rel="nofollow noreferrer">exoplanets.org</a>, but didn't find a column mentioning if the star is a binary. </p>

CC BY-SA 4.0
2019-12-05T16:19:15.387Z
@antispinwards I looked at exoplants.org, but didn't find any column indicating the number of stars in the system. I'll check out the NASA archive
usernumber
<exoplanet><binary-star><planetary-systems>
How many exoplanets have been found around binary stars?
usernumber
# How many exoplanets have been found around binary stars?

(Asked by: username_0 on 2019-12-05)

[This XKCD whatif](https://what-if.xkcd.com/150/) talks about circumbinary and [the other kind of] exoplanets. How many such exoplanets have actually been discovered?
[![enter image description here](https://i.sstatic.net/8x6ip.png)](https://i.sstatic.net/8x6ip.png)

I tried to look it up at [exoplanets.org](http://exoplanets.org/), but didn't find a column mentioning if the star is a binary.

**Tags:** exoplanet, binary-star, planetary-systems

> **Comments:**
> **username_0**: @antispinwards I looked at exoplants.org, but didn't find any column indicating the number of stars in the system. I'll check out the NASA archive  

---

## 2 answers

### Answer by username_1 on 2019-12-05. Score: 8 | Accepted answer

Go to the exoplanets.org database.

Top left hand dropdown menu - select "Stars"

You get a table listing all the known stars with exoplanets.

Click on the big plus sign in the top right hand of the table and select "Binary Flag"

This will now show a boolean flag that indicates if the star is known to be part of a binary (or multiple) system.

In the FILTER window at the top of the page, just type "BINARY" and the table will just show binary stars.

It is possible to export the table as a csv file using the "export" button at the top right. Counting the number of lines with the BINARY flag indicates that as of December 2019, there are 511 known exoplanets around binary stars.

> **Comments:**
> **username_0**: Does the database also indicate which planets are circumbinary and which planets are the other kind?  

---

### Answer by username_0 on 2020-02-28. Score: 1

[A recent paper](https://arxiv.org/abs/2002.12006) suggests that there are possibly more planets around binary stars than we have been able to detect because of observational biases. This means that there are more planets in binary systems than what we have discovered. From [exoplanet.eu](http://exoplanet.eu/planets_binary/)

> until recently, observational surveys, especially those relying on the radial velocity method, had been strongly biased against binaries

and

> for many cases, the binarity of the system was not known at the time of the exoplanet's discovery and was established by later observational campaigns. This means that there should still be a potentially large population of exoplanet-hosting "single" stars that are in fact members of a (yet undetected) multiple system.

However, the formation of planets is impeded, and any planets are more likely to be thrown out of the system when the separation between both stars is less than 100 AU. So the fraction of binary systems with planets should be smaller than the fraction of single stars with planets.

Another [recent paper](https://arxiv.org/abs/2002.11734) addresses the question of the frequency of planets in binary star systems based on data from Gaia's second release. Around close binaries, there are very few planets. However, there seem to be many planets around binaries with a white dwarf. So how many planets are around binary stars seems to depend on the geometry of the binary star system.

---

On a side note, the "other kind" of planet in the xkcd strip is referred to as a "circumstellar planet".


---

