<p>I don't know about names for the planets, specifically, but the orbits are called <a href="https://en.wikipedia.org/wiki/Binary_star#Planets">S-type and P-type</a>:</p>

<ul>
<li><p><strong>S-type</strong>: The planet orbits around one star, and the host star has a binary companion (i.e., "the other kind" in the XKCD comic)</p></li>
<li><p><strong>P-type</strong>: The planet orbits around both stars of the binary</p></li>
</ul>

CC BY-SA 3.0
2016-05-24T22:15:05.260Z
I propose the name "circumunary planet". It would be usable for both planets in systems like ours and in binary systems. You could refer to "the circumunary planet of Alpha Centauri B in the Alpha Centauri binary star system" for example, and you could also say "Earth is a circumunary planet of the sun in the solar system, a unary star".
called2voyage
CC BY-SA 3.0
2016-05-24T22:16:05.013Z
All planets of unary stars would be circumunary by definition, but planets in binary star systems could be either circumunary or circumbinary.
called2voyage
CC BY-SA 3.0
2016-05-24T22:19:50.297Z
Also, is it possible there are some objects which are gravitationally bound to a binary system but which technically revolve around neither star?
called2voyage
CC BY-SA 3.0
2016-05-24T22:55:17.927Z
@called2voyage:   Objects can be in or in semi-stable orbits around the various Lagrangian points.
ThePopMachine
CC BY-SA 3.0
2016-05-24T22:56:53.327Z
Yes, that's what I'm referring to, I'm just not sure how stable they would be
called2voyage
CC BY-SA 3.0
2016-05-25T15:18:30.247Z
in a binary system a Lagrange point (L4 or 5) could be stable, around the smaller of the 2 stars, not the larger (obviously).    The star ratio of mass has to be about 25 to 1 though.   http://astronomy.stackexchange.com/questions/11389/orbits-in-a-binary-star-system
userLTK
CC BY-SA 3.0
2016-05-25T16:47:37.273Z
@userLTK Thanks, so we do have another type of planet to consider besides circumbinary and circumunary.
called2voyage
CC BY-SA 3.0
2016-05-24T22:11:17.653Z
2016-05-24T22:11:17.653Z
J. O'Brien Antognini
<p>Astronomy currently only gives us the names circumbinary (left picture) and Trojan planet (unpictured, planet is around a Lagrange point), but from circumbinary we can extrapolate other names:</p>

<ul>
<li>circumunary - revolves around one star</li>
<li>circumtrinary/circumternary - revolves around a trinary/ternary star system</li>
</ul>

<p>Technically, there is another term that actually has some use: circumsystem. This is used for objects that revolve around a multiple star system regardless of the number of stars within the system.</p>

CC BY-SA 4.0
2020-12-17T19:04:52.383Z
The problem with this nomenclature is you want to distinguish between planets in binary systems and those that are not. I realise that - the "planet Alpha Cen Bb" makes this obvious, but that doesn't help when referring to them as a class.
ProfRob
CC BY-SA 4.0
2020-12-17T19:59:22.420Z
@RobJeffries I realize "circumunary planets of binary systems" is a bit of a mouthful, but at least more concise than "planets which orbit only one star of a binary system".
called2voyage
CC BY-SA 4.0
2020-12-17T20:02:42.963Z
But not more concise than "s-type exoplanet".
ProfRob
CC BY-SA 4.0
2020-12-17T20:04:21.793Z
@RobJeffries True, though I thought strictly speaking those were considered types of orbits not types of planets, so wouldn't that be "exoplanets in s-type orbits" in the strictest sense?
called2voyage
CC BY-SA 3.0
2016-05-25T17:44:24.660Z
2016-05-25T17:44:24.660Z
called2voyage
<p><a href="http://what-if.xkcd.com/150/" rel="nofollow noreferrer">This XKCD what-if</a> talks about rainbows on planets in a binary star system.   It points out that there are two types:</p>
<ul>
<li><em><strong>circumbinary</strong></em> planets, where the planet orbits far from and around both stars</li>
<li><em><strong>[the other kind of planet]</strong></em>, where the planet orbits one of the stars and the other star is distant.</li>
</ul>
<p><a href="https://i.sstatic.net/gSX15.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/gSX15.png" alt="enter image description here" /></a></p>
<h1>What is the proper name for [the other kind of planet] ?</h1>

CC BY-SA 3.0
2016-05-24T21:24:53.030Z
The term I usually see is "non-circumbinary". I wonder if there is a better term.
called2voyage
CC BY-SA 3.0
2016-05-25T17:29:10.240Z
I would have thought "circumstellar", as it orbits a single star and it sounds better than "circumunary".
zibadawa timmy
CC BY-SA 3.0
2016-05-25T17:47:20.313Z
@zibadawatimmy "circumstellar" is also used for "circumsystem" objects though which orbit around multiple stars.
called2voyage
<planet><exoplanet><binary-star><terminology>
What's the name for [the other kind of planet] in a binary star system?
ThePopMachine
# What's the name for [the other kind of planet] in a binary star system?

(Asked by: username_0 on 2016-05-24)

[This XKCD what-if](http://what-if.xkcd.com/150/) talks about rainbows on planets in a binary star system. It points out that there are two types:

* ***circumbinary*** planets, where the planet orbits far from and around both stars
* ***[the other kind of planet]***, where the planet orbits one of the stars and the other star is distant.

[![enter image description here](https://i.sstatic.net/gSX15.png)](https://i.sstatic.net/gSX15.png)

# What is the proper name for [the other kind of planet] ?

**Tags:** planet, exoplanet, binary-star, terminology
> **Comments:**
> **username_1**: The term I usually see is "non-circumbinary". I wonder if there is a better term.  
> **username_2**: I would have thought "circumstellar", as it orbits a single star and it sounds better than "circumunary".  
> **username_1**: @zibadawatimmy "circumstellar" is also used for "circumsystem" objects though which orbit around multiple stars.  

---

## 2 answers

### Answer by username_3 on 2016-05-24. Score: 9

I don't know about names for the planets, specifically, but the orbits are called [S-type and P-type](https://en.wikipedia.org/wiki/Binary_star#Planets):

* **S-type**: The planet orbits around one star, and the host star has a binary companion (i.e., "the other kind" in the XKCD comic)
* **P-type**: The planet orbits around both stars of the binary

> **Comments:**
> **username_1**: I propose the name "circumunary planet". It would be usable for both planets in systems like ours and in binary systems. You could refer to "the circumunary planet of Alpha Centauri B in the Alpha Centauri binary star system" for example, and you could also say "Earth is a circumunary planet of the sun in the solar system, a unary star".  
> **username_1**: All planets of unary stars would be circumunary by definition, but planets in binary star systems could be either circumunary or circumbinary.  
> **username_1**: Also, is it possible there are some objects which are gravitationally bound to a binary system but which technically revolve around neither star?  
> **username_0**: @called2voyage:   Objects can be in or in semi-stable orbits around the various Lagrangian points.  
> **username_1**: Yes, that's what I'm referring to, I'm just not sure how stable they would be  
> **username_4**: in a binary system a Lagrange point (L4 or 5) could be stable, around the smaller of the 2 stars, not the larger (obviously).    The star ratio of mass has to be about 25 to 1 though.   http://astronomy.stackexchange.com/questions/11389/orbits-in-a-binary-star-system  
> **username_1**: @userLTK Thanks, so we do have another type of planet to consider besides circumbinary and circumunary.  

---

### Answer by username_1 on 2016-05-25. Score: 2

Astronomy currently only gives us the names circumbinary (left picture) and Trojan planet (unpictured, planet is around a Lagrange point), but from circumbinary we can extrapolate other names:

* circumunary - revolves around one star
* circumtrinary/circumternary - revolves around a trinary/ternary star system

Technically, there is another term that actually has some use: circumsystem. This is used for objects that revolve around a multiple star system regardless of the number of stars within the system.

> **Comments:**
> **username_5**: The problem with this nomenclature is you want to distinguish between planets in binary systems and those that are not. I realise that - the "planet Alpha Cen Bb" makes this obvious, but that doesn't help when referring to them as a class.  
> **username_1**: @RobJeffries I realize "circumunary planets of binary systems" is a bit of a mouthful, but at least more concise than "planets which orbit only one star of a binary system".  
> **username_5**: But not more concise than "s-type exoplanet".  
> **username_1**: @RobJeffries True, though I thought strictly speaking those were considered types of orbits not types of planets, so wouldn't that be "exoplanets in s-type orbits" in the strictest sense?  

---

