# Under which circumstances could a planet have two visible suns?

In the story I'm making, it is important that there are two suns in the sky, going at different rythms (maybe the planet orbits one of them each year, and the other each four years, for instance), and the planet rotates, making it so that in regular patterns, let's say in the beginning of the cycle, both suns seem "together", from the planet, like one is eclipsing the other, but as times goes on, in the mid-day (considering the planet which is rotated yearly as reference), the other sun seems to lag behind, until at exactly half the cycle, just as one of the suns is exactly at mid-day position in one side of the planet, the other sun is also at mid-day position, but in the opposite side of the planet.

One thing I thought, which I don't know how possible it is, is that one of the suns is incredibly more massive than the other, and it's very far, so it's like the smaller sun orbits the big one, and the planet orbits the small one, just like earth orbits the sun, and the moon does the same with the earth. The planet I thought of is similar to earth in size (that can change, is not that important) and climate (that is important, I'd like seasons to feel similar and wildlife in general to be similar).

So that the sun that is close to the planet irradiates a similar ammount of light and heat to our sun, I think it may need to have a similar size, but, would the other sun need to be impossibly massive at that point, so that the small sun orbits it? I know technically both suns orbit each other and affect each other, but in order for the visible cycle I'm describing to happen, I think one would have to be more massive than the other, but I don't know if it would be so massive it would just not be a sun anymore, but would just collapse. If I make that sun smaller, would mean the small sun is even smaller, and the planet would have to be either smaller as well (but gravity would than be very different to earth, which I wouldn't like), or way closer to the small sun.

This is just one way I've thought about it, and I'm not married to that idea, my goal is to look for a way so that the cycle I describe is possible. Just to clarify, there is a magic system intended, but I want it to be completely independent from how this sun system works, if possible. I want it to be possible with the science we know, even if it's a very unlikely (but possible) scenario, so I'd like to avoid magic and science fiction altogether.

• The suns will rotate around common barycenter, and the planet can rotate around either of those suns, or the barycenter, if it's distant. Why do you think one sun should be much more massive than the other? Commented Dec 9, 2019 at 22:17
• A way of introducing other bright points of interest to the sky that could be described as a sun (if it’s identified as a Sun by characters who aren’t part of a science based story where they’re bobbing about in space physically looking at the star but are part of a ground based magic story) then it doesn’t necessarily have to be a star. An inward drifting gas giant with an orbit of perhaps 0.2 AU and an orbit of just a few days would still be seen an one of the brightest objects in the sky. Commented Dec 9, 2019 at 22:39
• Also, diameter doesn’t necessarily dictate gravitational strength. Commented Dec 9, 2019 at 22:45
• Not my field, so I am not confident enough to write an answer, but Wikipedia actually has a page on the potential habitability of binary star systems which might address much of your question. en.wikipedia.org/wiki/Habitability_of_binary_star_systems Commented Dec 10, 2019 at 7:27
• Maybe worthwhile to have a look at "Universe Sandbox" - AFAIK it lets you simulate a star system of your liking and see how that plays out. Commented Dec 11, 2019 at 22:11