<p>No,</p>
<p>In a circumbinary configuration the two stars are close together and close to the common centre of mass, and the planet moves in a wide orbit about both.</p>
<p>From the perspective of a planet, the motion of the star (or stars) is due to the rotation and orbit of the planet, and secondarily due to the actual motion of the stars relative to their centre of mass. Think how the sun moves daily from East to West (due to the rotation of the Earth) and yearly relative to the background stars (due to the orbit of the Earth). Your two suns will have the same basic motions.</p>
<p>The two stars will have similar motions,  daily (due to the rotation of the planet) and annually (due to the orbit of the planet).</p>
<p>In addition the two stars will be in orbit around each other, as a result of this orbit they will move sometimes further apart from each other in the sky and sometimes closer together.</p>
<p>So if the planet has an Earth-like rotation, you would see the two suns rising, moving across the sky and setting close together.  If you watched over several days you would notice that they moved closer together and then further apart.  The length of this cycle could be more or less, but would typically be about a week.  Over the course of the planet's &quot;year&quot; the two stars would move together across the background stars.</p>
<p>The further apart the two stars are, the slower their orbits will be. So if the two stars are able to move quickly in the sky, they would have to be very close to one another. And so could not be widely separated.  Indeed, if the two stars appear widely separated, it makes the circumbinary orbit difficult to maintain.  Stability of a circumbinary orbit depends on the two stars being close together.</p>
<p>A configuration in which the two stars are widely separated in the sky and then, over the course of a day come closer together and set together is not dynamically possible.</p>

CC BY-SA 4.0
2023-05-29T16:25:17.327Z
is such a system theoretically possible that the planet's orbit [CROSSES](https://www.dropbox.com/s/5dyxaolvzmfwseq/2suns_002.jpg?dl=0) the center of masses between the two suns?
ivan866
CC BY-SA 4.0
2023-05-29T16:48:21.810Z
No. That is not theoretically possible in a stable circumbinary configuration.
James K
CC BY-SA 4.0
2023-05-30T20:52:24.367Z
I wonder what I'll spend the quatloos on....
James K
CC BY-SA 4.0
2023-05-29T14:42:59.390Z
2023-05-29T17:26:46.747Z
2023-05-29T17:26:46.747Z
James K
<blockquote>
<p>Are there such circumbinary planet configurations that two suns move towards each other by the sky?</p>
<p>Is it possible that suns move towards each other (not necessarily in the opposite directions)? Such a configuration would cause interesting dusk and midday light cycles, in my opinion.</p>
</blockquote>
<p>Yes sure, absolutely!</p>
<p>If the circumbinary planet's orbit is in the same plane as the the binary's orbit, there will be regular eclipses as each passes behind the other. If one is bright and small, and the other dimmer and large, you may have a dim day, or weeks or months of them, depending on all the details (relative sizes and
their period.</p>
<p>You may also have contributions from light reflected from one star off the other star! In other words, if they are really close and even if there is no occultation/eclipse, you'll get color gradients across each star's disks.</p>
<p>Basically &quot;the sky's the limit&quot; :-)</p>

CC BY-SA 4.0
2023-05-29T09:01:49.053Z
No more of I think this answer is not useful, I'm not certain what the OP is asking, it's not clear, but this seems to answer the question "can two suns move around each other. I don't think it is useful to speculate on what you think the question ought to have been
James K
CC BY-SA 4.0
2023-05-29T10:07:07.367Z
@JamesK [I'll wager 100 quatloos](https://youtu.be/wV_UZ7GEJd8?t=54) that I've understood the "newcomer"'s question correctly. :-)
uhoh
CC BY-SA 4.0
2023-05-29T13:48:49.020Z
@uhoh that's a one interesting configuration, although something exotic and not strictly related to the question in general; i mean, obviously some geometrically bizarre configurations are possible, but the question is whether this is possible with normal conditions and normal suns
ivan866
CC BY-SA 4.0
2023-05-29T13:51:34.570Z
@JamesK i have made a clarifying update, as requested
ivan866
CC BY-SA 4.0
2023-05-29T16:34:36.353Z
@ivan866 I wrote that "the circumbinary planet's orbit is in the same plane as the the binary's orbit". This is the opposite of a bizarre combination, it's probably *the most likely combination*. Everything is in a single plane. I'll delete the graphic because I think you looked at the picture but didn't read the words.
uhoh
CC BY-SA 4.0
2023-05-29T17:08:55.523Z
@uhoh the picture was NOT indeed illustrating the answer itself
ivan866
CC BY-SA 4.0
2023-05-29T22:32:59.583Z
@ivan866 the picture perfectly illustrated the part of the answer directly above it: "You may also have contributions from *light reflected from one star off the other star!* In other words, if they are really close and even if there is no occultation/eclipse, you'll get color gradients across each star's disks."
uhoh
CC BY-SA 4.0
2023-05-30T16:51:58.883Z
From [chat](https://chat.stackexchange.com/rooms/146351/discussion-between-pm-2ring-and-ivan866), it seems that ivan wants a scenario where one sun sets in the west while the other sun sets in the east, at the same time.
PM 2Ring
CC BY-SA 4.0
2023-06-02T04:21:24.427Z
@JamesK per PM 2Ring's comment and [chat](https://chat.stackexchange.com/rooms/146351/discussion-between-pm-2ring-and-ivan866) you may have won yourself  100 quatloos! Don't spend it all in one place :-)
uhoh
CC BY-SA 4.0
2023-05-29T07:18:46.313Z
2023-05-29T16:36:32.767Z
2023-05-29T16:36:32.767Z
uhoh
<p>At least one theoretical solution exists, involving a triple star orbiting a figure-8 shape. And from the P-type planet one of the suns will be seen as setting in a different direction.</p>

CC BY-SA 4.0
2023-06-01T13:04:21.247Z
Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer).
Community
CC BY-SA 4.0
2023-05-30T07:33:12.767Z
2023-05-30T07:33:12.767Z
ivan866
<p>Is it possible that suns move towards each other (not necessarily in opposite directions)? Such a configuration would cause interesting dusk and midday light cycles, in my opinion.</p>
<p>Basically the question is about whether it is possible that one of the suns has a clockwise orbit (relative to the planet's pole) while the second sun has the counterclockwise orbit, which will be seen on the sky as follows:</p>
<p><a href="https://i.sstatic.net/sWtHY.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/sWtHY.png" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2023-05-28T23:13:05.233Z
Please clarify your question.
ProfRob
CC BY-SA 4.0
2023-05-29T07:19:56.303Z
The can't *only* move towards eachother because sooner or later they would hit each other. And then you'd have a very interesting dusk... Please explain what you mean more clearly
James K
CC BY-SA 4.0
2023-05-29T07:26:23.897Z
@JamesK surely you understand that when seen from a planet, two celestial objects move toward each other they don't generally hit each other. They generally eclipse or occult. Mars doesn't [hit the Moon twice a year](https://astronomy.stackexchange.com/q/40532/7982) for example.
uhoh
CC BY-SA 4.0
2023-05-29T07:36:25.937Z
Yes, but in that case the objects would have to subsequently move away from each other. And in this configuration we would normally say that that the move around each other. I don't think the OP is asking if the stars sometimes move around each other. But I don't know what they are asking that's why the question is unclear.
James K
CC BY-SA 4.0
2023-05-29T13:51:04.687Z
@ProfRob i made an update as requested
ivan866
CC BY-SA 4.0
2023-05-29T14:34:46.040Z
Binary stars stay in line with their centre of mass (barycentre), so they can't orbit in opposite directions. Please see my answer on our sister site: https://physics.stackexchange.com/a/558847/123208
PM 2Ring
CC BY-SA 4.0
2023-05-29T16:09:29.330Z
@PM2Ring are there any configurations NOT involving binary stars as the system's center of masses, perhaps very large but distant second sun?
ivan866
CC BY-SA 4.0
2023-05-29T18:08:38.190Z
Sorry, @ivan I don't fully understand your last comment. A circumbinary planet is in a P-type orbit around the Pair of stars, a circumstellar planet is in an S-type orbit around a Single star, see the diagram here: https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems Stars are much more massive than planets, so their mass totally dominates the system. Eg, in our Solar System, the Sun has ~1000 times the mass of Jupiter, which has ~300 times the  mass of the Earth.
PM 2Ring
CC BY-SA 4.0
2023-05-30T06:13:59.447Z
@PM2Ring if that so, my question is not about solely circumbinary systems then, but about those which may potentially have two proximal stars seen on their sky, also
ivan866
CC BY-SA 4.0
2023-05-30T06:31:06.477Z
@ivan Ok, but it's a bit too late to change your question now, since that would invalidate the 2 existing answers.
PM 2Ring
CC BY-SA 4.0
2023-05-30T06:31:44.727Z
Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/146351/discussion-between-pm-2ring-and-ivan866).
PM 2Ring
CC BY-SA 4.0
2023-05-30T06:31:57.470Z
@PM2Ring this is why i am not changing it, precisely
ivan866
<planet><orbital-mechanics><sunrise><skyfield>
Are there such circumbinary planet configurations that two suns move towards each other by the sky?
ivan866
# Are there such circumbinary planet configurations that two suns move towards each other by the sky?

(Asked by: username_0 on 2023-05-28)

Is it possible that suns move towards each other (not necessarily in opposite directions)? Such a configuration would cause interesting dusk and midday light cycles, in my opinion.

Basically the question is about whether it is possible that one of the suns has a clockwise orbit (relative to the planet's pole) while the second sun has the counterclockwise orbit, which will be seen on the sky as follows:

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

**Tags:** planet, orbital-mechanics, sunrise, skyfield

> **Comments:**
> **username_1**: Please clarify your question.  
> **username_2**: The can't *only* move towards eachother because sooner or later they would hit each other. And then you'd have a very interesting dusk... Please explain what you mean more clearly  
> **username_3**: @JamesK surely you understand that when seen from a planet, two celestial objects move toward each other they don't generally hit each other. They generally eclipse or occult. Mars doesn't [hit the Moon twice a year](https://astronomy.stackexchange.com/q/40532/7982) for example.  
> **username_2**: Yes, but in that case the objects would have to subsequently move away from each other. And in this configuration we would normally say that that the move around each other. I don't think the OP is asking if the stars sometimes move around each other. But I don't know what they are asking that's why the question is unclear.  
> **username_0**: @username_1 i made an update as requested  
> **username_4**: Binary stars stay in line with their centre of mass (barycentre), so they can't orbit in opposite directions. Please see my answer on our sister site: https://physics.stackexchange.com/a/558847/123208  
> **username_0**: @PM2Ring are there any configurations NOT involving binary stars as the system's center of masses, perhaps very large but distant second sun?  
> **username_4**: Sorry, @ivan I don't fully understand your last comment. A circumbinary planet is in a P-type orbit around the Pair of stars, a circumstellar planet is in an S-type orbit around a Single star, see the diagram here: https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems Stars are much more massive than planets, so their mass totally dominates the system. Eg, in our Solar System, the Sun has ~1000 times the mass of Jupiter, which has ~300 times the  mass of the Earth.  
> **username_0**: @PM2Ring if that so, my question is not about solely circumbinary systems then, but about those which may potentially have two proximal stars seen on their sky, also  
> **username_4**: @ivan Ok, but it's a bit too late to change your question now, since that would invalidate the 2 existing answers.  
> **username_4**: Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/146351/discussion-between-pm-2ring-and-username_0).  
> **username_0**: @PM2Ring this is why i am not changing it, precisely  

---

## 3 answers

### Answer by username_2 on 2023-05-29. Score: 1

No,

In a circumbinary configuration the two stars are close together and close to the common centre of mass, and the planet moves in a wide orbit about both.

From the perspective of a planet, the motion of the star (or stars) is due to the rotation and orbit of the planet, and secondarily due to the actual motion of the stars relative to their centre of mass. Think how the sun moves daily from East to West (due to the rotation of the Earth) and yearly relative to the background stars (due to the orbit of the Earth). Your two suns will have the same basic motions.

The two stars will have similar motions, daily (due to the rotation of the planet) and annually (due to the orbit of the planet).

In addition the two stars will be in orbit around each other, as a result of this orbit they will move sometimes further apart from each other in the sky and sometimes closer together.

So if the planet has an Earth-like rotation, you would see the two suns rising, moving across the sky and setting close together. If you watched over several days you would notice that they moved closer together and then further apart. The length of this cycle could be more or less, but would typically be about a week. Over the course of the planet's "year" the two stars would move together across the background stars.

The further apart the two stars are, the slower their orbits will be. So if the two stars are able to move quickly in the sky, they would have to be very close to one another. And so could not be widely separated. Indeed, if the two stars appear widely separated, it makes the circumbinary orbit difficult to maintain. Stability of a circumbinary orbit depends on the two stars being close together.

A configuration in which the two stars are widely separated in the sky and then, over the course of a day come closer together and set together is not dynamically possible.

> **Comments:**
> **username_0**: is such a system theoretically possible that the planet's orbit [CROSSES](https://www.dropbox.com/s/5dyxaolvzmfwseq/2suns_002.jpg?dl=0) the center of masses between the two suns?  
> **username_2**: No. That is not theoretically possible in a stable circumbinary configuration.  
> **username_2**: I wonder what I'll spend the quatloos on....  

---

### Answer by username_3 on 2023-05-29. Score: 1

> Are there such circumbinary planet configurations that two suns move towards each other by the sky?
>
> Is it possible that suns move towards each other (not necessarily in the opposite directions)? Such a configuration would cause interesting dusk and midday light cycles, in my opinion.

Yes sure, absolutely!

If the circumbinary planet's orbit is in the same plane as the the binary's orbit, there will be regular eclipses as each passes behind the other. If one is bright and small, and the other dimmer and large, you may have a dim day, or weeks or months of them, depending on all the details (relative sizes and
their period.

You may also have contributions from light reflected from one star off the other star! In other words, if they are really close and even if there is no occultation/eclipse, you'll get color gradients across each star's disks.

Basically "the sky's the limit" :-)

> **Comments:**
> **username_2**: No more of I think this answer is not useful, I'm not certain what the OP is asking, it's not clear, but this seems to answer the question "can two suns move around each other. I don't think it is useful to speculate on what you think the question ought to have been  
> **username_3**: @JamesK [I'll wager 100 quatloos](https://youtu.be/wV_UZ7GEJd8?t=54) that I've understood the "newcomer"'s question correctly. :-)  
> **username_0**: @username_3 that's a one interesting configuration, although something exotic and not strictly related to the question in general; i mean, obviously some geometrically bizarre configurations are possible, but the question is whether this is possible with normal conditions and normal suns  
> **username_0**: @JamesK i have made a clarifying update, as requested  
> **username_3**: @username_0 I wrote that "the circumbinary planet's orbit is in the same plane as the the binary's orbit". This is the opposite of a bizarre combination, it's probably *the most likely combination*. Everything is in a single plane. I'll delete the graphic because I think you looked at the picture but didn't read the words.  
> **username_0**: @username_3 the picture was NOT indeed illustrating the answer itself  
> **username_3**: @username_0 the picture perfectly illustrated the part of the answer directly above it: "You may also have contributions from *light reflected from one star off the other star!* In other words, if they are really close and even if there is no occultation/eclipse, you'll get color gradients across each star's disks."  
> **username_4**: From [chat](https://chat.stackexchange.com/rooms/146351/discussion-between-pm-2ring-and-username_0), it seems that ivan wants a scenario where one sun sets in the west while the other sun sets in the east, at the same time.  
> **username_3**: @JamesK per username_4's comment and [chat](https://chat.stackexchange.com/rooms/146351/discussion-between-pm-2ring-and-username_0) you may have won yourself  100 quatloos! Don't spend it all in one place :-)  

---

### Answer by username_0 on 2023-05-30. Score: -1

At least one theoretical solution exists, involving a triple star orbiting a figure-8 shape. And from the P-type planet one of the suns will be seen as setting in a different direction.

> **Comments:**
> **username_5**: Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer).  

---

