Viability of Many Suns

This is the first of a thread of related posts on a hypothetical alternate universe/Light Plane.

Other posts from this thread are here:

How To Make an Earth with 27 Suns Work, Attempt Two: Orbital Stability

(Will be updated as more are asked.)

I have a heliocentric stellar system with 27 stars ranging in mass from blue giants to white dwarfs. There's also a few main sequence stars thrown in for good measure. I also want an earth like planet to exist in this system for about 7 billion years. It only has to orbit one of the stars, not all of them. The stars can orbit one another in concentric rings or in binary-like systems. You can rearrange these suns--make them any size/type/distance/orbit pattern you like--so long as there are 27 of them. I don't want any black holes.

They must be within 1 light minute-5 light-days of distance. They must also be in a perfectly stable orbital arrangement.

The planet must have an oxygen atmosphere and must be solid. (not a gaseuous planet. Solid core, molten mantle and solid crust. The orbits must be long-term stable and the system **must have the specified number of suns. There must be at least one white dwarf and at least one giant blue star. Assume for all intents and purposes that the suns will live for the regular lifespan.


How would this be possible? Manipulate the suns, planet, orbits, arrangements of orbits, shapes of orbits, times, distances, sun types, gravity, planet size, planet gravity, even the gravity of the universe, and add/take away moons as needed as needed. I don't know how to arrange the stars and this planet in such a way that I can get the longterm stability that I'm after. Can they be arranged in a stable way and if not, what would need to change to make them stable?

Quick note:

VERY Science based answers only please. Handwavium/unobtanium/it's magic answers NOT acceptable. Feel free to add/remove any planets nearby and do the same with moons: so long as I get my key planet. I would prefer having at least 1 moon, but it's okay if I can't have one. The planet will be pretty white/reflective and have lots of ozone to protect it from all of the solar radiation, as well as a unique magnetic field.

Additional info:

Don't bother:

About temperatures. Let the planet fry. I just need orbital stability.

Magnetics: This will be left for a later post, but assume that the planet has a super-powerful magnetic field to protect it from the radiation of all 27 suns.

Gravity: Manipulate as you see fit (no making gravity stronger.) But you can (ONLY IF YOU MUST TO MAKE THIS SYSTEM WORK) make gravity UP TO five times weaker.

Black Holes: Just assume that there are none. Don't add any. No black holes, period.


If downvoting/VTC'ing, please leave a comment as to

  • why


  • exactly how to fix

And thank you to the Sandbox for your help.

Final edit

Note to close-voters/mods: I'd like this closed as a duplicate of "How To Make an Earth with 27 Suns Work, Attempt Two: Orbital Stability" since the question is redone and answered there, so anyone visiting this page will be redirected to the question with the full answer.

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    $\begingroup$ Considering the 3 body problem is basically unsolvable, I don't know about the 27 body problem... Very interested to see if anyone has a good science answer to this. $\endgroup$
    – AndyD273
    May 10, 2018 at 14:54
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    $\begingroup$ Looks like you edited with sole purpose of invalidating already posted answers. This is generally "strongly discouraged" on Stack Exchange network and may lead to downvotes, edit reverts etc. $\endgroup$
    – Mołot
    May 10, 2018 at 15:33
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    $\begingroup$ Sometimes the only way is to accept answers saying "Can not be", and ask new one, starting with "Thanks to answers to [question link] I'm asking similar question, with corrected constraints". $\endgroup$
    – Mołot
    May 10, 2018 at 15:46
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    $\begingroup$ @Anonymous even if you follow Mołot's advice, be aware that no matter how much you modify physics, the requirements for your setup will not be satisfiable through science. If you make gravity weaker the system grows larger. Make it stronger, and stars will need less mass to go Nova. You would end up needing to modify things such as the speed of light, composition of atoms... In the end you would have a universe that is nothing like our own. $\endgroup$ May 10, 2018 at 15:51
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    $\begingroup$ Anonymous - it may be helpful to ask a new question describing what effect you want to achieve, and what feasible astronomical configuration can get you that. I'm guessing that the desired end result is something like an Earthlike planet with 27 suns (or sun-like objects) in its the sky, likely with specific colors - maybe something even more specific? It's quite possible that such a thing is achievable, just not in the manner you stated here... $\endgroup$
    – G0BLiN
    May 10, 2018 at 17:01

5 Answers 5


How would this be possible?

It would not, for a range of reasons.

For the stars to coexist in such a system, they would have to be arranged in a way similar to planets in our own solar system. They cannot share orbits - two planets sharing an orbit, even in lagrangian points, are not stable over geological time. But five light-days is just too tight. Consider Sagittarius A* and its orbiting stars. There aren't even a dozen of them. S2's apoapsis (furthest distance from parent body) is about five light-days away from the central black hole.

Sagittarius A*

In the beginning of our own solar system, Earth and Theia shared an orbit for a few million years. It ended up with them colliding, resulting in Theia's destruction. The debris from the impact became our Moon.

Considering stars, the larger ones might throw the smaller ones out of the system by gravity slingshot. There would still be lots of collisions, though. If such an impact happened involving stars, you would have star mergers. Given the amount of stars and masses involved (you said blue giants), this might result in the formation of supergiants, which will eventually go out in no more than thrirty million years as supernovae. Those are very energetic events:

However big you think supernovae are, they're bigger than that.

Here's a question to give you a sense of scale:

Which of the following would be brighter, in terms of the amount of energy delivered to your retina:

  • A supernova, seen from as far away as the Sun is from the Earth, or

  • The detonation of a hydrogen bomb pressed against your eyeball?

Applying the physicist rule of thumb suggests that the supernova is brighter. And indeed, it is ... by nine orders of magnitude.

Nine orders of magnitude means one billion times greater. Everytime you double the distance the energy output is quartered, but... at five light days away - approximately 865 AU - a supernova would still hit every single point on the surface of the planet with the power of more than fifteen thousand hydrogen bombs. And that is just one supernova.

In the end this setup will vaporize the planet real quick. Just saying.

  • $\begingroup$ Edited to loosen constraints. Hope that helps $\endgroup$ May 10, 2018 at 15:27
  • $\begingroup$ Also assume that supernovae won't happen for several billion years longer. I know, I know, it's impossible, but we're talking hypothetically unusually long-lived stars. Just pretend I'm channeling extra hydrogen into them. $\endgroup$ May 10, 2018 at 15:31
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    $\begingroup$ @Anonymous if you pump extra hydrogen in them you will just make them go into supernovae faster. In general, the more massive the star, the shorter its life. Also the distance increase you did with your edit to the question is negligible, given the energies involved. Sorry, but there is no science-based scenario in which this could happen. If you want to work with this world you are creating - whether you are writing a book, making a game, GM'ing a tabletop RPG session - the only way to explain this is magic. $\endgroup$ May 10, 2018 at 15:35
  • $\begingroup$ Thanks for the advice. I'm going to accept this answer and then start a new question in this series on an updated version of this post. $\endgroup$ May 10, 2018 at 15:49
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    $\begingroup$ @AndyD273 no. It's nor about the arrangement of the stars, it's about having just too much stuff for too little space. $\endgroup$ May 10, 2018 at 16:15
  1. it is impossible for an Earth like planet to exist in the same solar system as 27 stars including at least one blue giant and at least one white dwarf for seven billion years.

    For one reason, Earth is about 4,600,000,000 years old and didn't have enough oxygen in the atmosphere to be habitable for humans for over half that time. So I guess you mean that the planet will become habitable for humans after life has been evolving on it for several billion years and it will still be habitable at an age of seven billion years.

    Main sequence stars eventually become red giant stars, vastly increasing their luminosity and swallowing their inner planets, and then become white dwarf stars, or neutron stars, or stellar black holes. Becoming white dwarf stars, or neutron stars, or stellar black holes involves the stars losing a significant proportion of their masses.

    In the best case scenario that involves shells of gas and plasma expanding from those stars at great speeds. It is easy to believe that could result in devastating every single planet in the system when they are struck by those shells of expanding matter.

    In the worst case scenario that involves one of the stars becoming a nova or even a supernova. Either would sterilize any planets with life and a supernova would vaporize those planets.

    A blue giant would have a main sequence lifetime of just tens of millions of years.

    So your solar system could not last for seven billion years but for only about 0.001 to 0.01 times that long.

    Thus the only possible way for your solar system to exist and have one or more habitable (and thus billions of years old) planets in it would be if super advanced aliens assembled it out of preexisting stars and planets. And only if it didn't matter to them how long the planets remained habitable.

  2. a solar system with 27 stars would probably not be stable for seven billion years. Star systems with a single star, or with two stars, are very common. Star systems with three or more stars are a minority.

    multiple star systems with stable orbits that can last for billions of years are hierarchical, with the outer stars orbiting at distances several times the distances that in the inner stars orbit.

    For example, two stars might orbit each other at a distance of 0.10 AU, two other stars might orbit each other at a distance of 0.12 AU, and the two pairs might orbit each other at distances ranging from 13.1 AU to 15.4 AU.

    There seem to be two septenary systems (seven stars) known, Nu Scorpii and Ar Cassiopeiae.

    There is a site called PlanetPlanet that has, among other things, many discussions of fictional and imaginary star systems.

    The ultimate solar system section has posts devoted the designing imaginary solar systems with the most stars and the most habitable (for humans) planets.

    They lead up to post # 6 "A System with Many Stars", involving an imaginary star system with 16 stars and 384 to 576 habitable planets in the habitable zones of the 16 stars (24 to 36 habitable planets for each star).

    And the next post, "The Biggest Tragedy in the History of the Universe" describes how that solar system would fall apart within a billion years and most of the habitable planets would be destroyed.

    I think that makes it clear that a 27 star system would suffer an even quicker fate.

So super advanced aliens wouldn't assemble your 27 star system and put already habitable and life bearing planets in it if they wanted those life bearing planets to have long future histories. Maybe the super advanced aliens would build such a star system to test whether intelligent life on some of the planets could advance fast enough to predict disaster and manage to escape that disaster. I can imagine your solar system being created as a bet between two bored godlike beings.

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    $\begingroup$ Even if you managed to arrange this system artificially, it would still become unstable faster than life could evolve in a planet. $\endgroup$ May 10, 2018 at 17:09
  • $\begingroup$ @Renan Maybe the super advanced aliens who move 27 stars to form a solar system that could never form naturally would also move planets billions of years old that already have advanced life into that artificial solar system, as I said in my last paragraph. Or the super advanced aliens might terraform a bunch of the planets in the artificial solar system and seed them with advanced lifeforms from other solar systems. $\endgroup$ May 11, 2018 at 20:42
  • $\begingroup$ I believe the time between setting the planet there and an irreversible disaster would range from hours to days. As soon as I get the opportunity I will reinstall Universe Sandbox 2 on my computer and set up this system. I believe in the first week we will see some stars being slingshot away from the system, which will change all initial orbits. In the first year we should see a nova. $\endgroup$ May 11, 2018 at 21:17
  • $\begingroup$ Thanks for the links to my blog (planetplanet.net)! But please note that there is in fact a way to make this system work, by placing rings of stars around a very massive black hole as in this post: planetplanet.net/2018/03/21/asimov-kalgash-take2. I wrote a full answer but I'm afraid people have already given up on this being possible when it's not. $\endgroup$ May 12, 2018 at 13:44

These constraints are so aggressive as to be ridiculous:

27 gravity wells in an orbit stable enough to last for 7 billion years, but close enough together to allow for a planet to orbit them all; and having an orbiting planet that has very little temperature variability so that it can be Earthlike.

The very science-based answer is to rethink your constraints.

You might be able to have a heliocentric solar system with an Earthlike planet, but it almost certainly means the stars will have to be so close that they'll spiral into each other long before 7 billion years would elapse.

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    $\begingroup$ I meant that the planet orbits ONE OF the suns. Thanks for pointing out. I'll edit above $\endgroup$ May 10, 2018 at 15:24
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    $\begingroup$ Even then BigK is right, stars close enough to be seen as suns would wreck havoc on the orbital stability of your planet, and probably fry it as well. $\endgroup$
    – Mołot
    May 10, 2018 at 15:28
  • $\begingroup$ @Mołot at five light-days, no - three light-days out, and the Sun should be as bright as the full Moon on Earth (way smaller of course). Enough to read by, but no more. Eight light-hours from a G0 star and the planet would be frozen like Pluto. $\endgroup$
    – LSerni
    May 11, 2018 at 22:07

In contrast to the other answers, your setup IS possible (at least, most parts of it). And, before you go thinking I'm nuts, I will mention that I am an astrophysicist who works on celestial mechanics and planet formation. (for instance, see my website here).

Let me explain.

Let's start with planets orbiting a star. In systems like the Solar System, each planet has its own orbit and successive orbits can't be too close together or the system will go unstable (details here).

Two planets can share the same orbit in some situations. That is called a co-orbital setup, and the most common one has two planets in their common Lagrande 4/5 points (see here).

It can go further. Rings of planets that are evenly-spaced are stable for long timescales if they are appropriately set up (details here). It looks like this:

image from this blog post: https://planetplanet.net/2017/05/03/the-ultimate-engineered-solar-system/

There are 42 Earth-mass planets at 1 AU orbiting a Sun-like star. I was super skeptical of this idea, so I ran billion year long simulations (in computer time of course) and it is totally stable. There are some restrictions: the planets must be equal-mass (within a given ring) and evenly-spaced.

To adapt this to your many-star system, we need to add 3 ingredients: 1. We need to make stars be like the "planets" by including something much more massive than them in the center; and 2. If you want different types of stars then you'll need multiple rings; and 3. Your planet can also orbit the massive thing like an asteroid to the stars' "planets"

It turns out I already did your setup (pretty much) in a recent blog post. I put a super-massive black hole in the center. Then I laid down rings of stars analogous to the ring of planets in the image above. Here is what the system I built that was most similar to your setup looked like:

from this blog post: https://planetplanet.net/2018/03/21/asimov-kalgash-take2/

My goal was to keep a planet in constant dalyight (like in Asimov's story Nightfall). So the details are different than your idea but the jist is the same.

So here is how to set this up. Stick a 1 million Solar-mass black hole in the center. Take as many stars as you want, but make sure there are at least 7 of each specific type. Make a ring of each set of stars, with successive rings spaced out sufficiently to maintain stability (see here). Throw your planet in there on its own orbit, in between rings or interior/exterior to the rings. Or the planet could orbit one of the stars in one of the rings if you prefer.

And boom, there you go! Celestial mechanics can work nicely if you set it up just right. Of course, such a system would be prone to breaking if there were any significant perturbations. But left to itself it's totally stable -- to reiterate, I've checked with N-body simulations.

  • $\begingroup$ "No black holes, period." Is there any way to do this without a black hole? $\endgroup$ May 13, 2018 at 22:48
  • $\begingroup$ Oops, I missed the no black holes part. Let's see -- it's borderline. If you put a very massive star (say, a 50 solar mass O star) in the center you can have just-barely stable rings of tiny red stars (8% of the Sun's mass) with seven stars per ring. But you can't go any higher in stellar mass without jumping to a ridiculously massive star that could only plausibly be a black hole $\endgroup$ May 14, 2018 at 14:27
  • $\begingroup$ Thanks for the info. Like I stated above, I'm modifiying the question to post in the new Sandbox (hope it's posted soon.) I'd appreciate your feedback there. Feel free to answer it once it is posted on main. $\endgroup$ May 14, 2018 at 15:00
  • $\begingroup$ Given that the solar system moves in the galaxy, isn't "Of course, such a system would be prone to breaking if there were any significant perturbations." never given? Your highly symmetrical version seems to work only in an otherwise empty universe $\endgroup$
    – SK19
    May 14, 2018 at 16:20
  • $\begingroup$ SK19 -- no, it's not all that fragile. Typical encounters between stars are distant enough that there isn't any obvious concern from external perturbations. For instance, the Solar System probably never had another star within a few hundred Astronomical Units, and that sort of distance would not destabilize the rings $\endgroup$ May 14, 2018 at 23:06

Not going to happen.

27 stars ranging in mass from blue giants to white dwarfs. There's also a few main sequence stars thrown in for good measure. I also want an earth like planet to exist in this system for about 7 billion years.

That's it right there -- blue giants don't live for seven billion years. To be able to have a B or A luminosity, they must burn fuel like crazy, and they don't last.

You can try aiming for seven million, and this part would work (then there are other difficulties, as others have indicated).


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