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Red dwarves are the most common stars in our galaxy, if not the whole universe. They are small--the largest don't exceed one-half of a solar mass--but scientists still believe in their potential for habitability due simply to their lifespan. We don't exactly know how long a red dwarf can live. Some say hundreds of billions of years. Some even say trillions. But the point stands that they can support life for far longer than our sun can.

But this raises its own problems. Red dwarves are so dim that for any planets orbiting them to sustain life, they have to do so at a very, very, very, very, very, very, very, very, very, very, very, very close distance--close enough for one side to be eternal day and another to be eternal night. (Not at all Earthlike, if you ask me.)

I've been advised, again and again, that pitting main-sequence stars in a trinary P-style orbit just isn't feasible. Such an arrangement won't allow for a stable orbit. But the smaller red dwarves don't seem to have that problem. So my question is this--how many red dwarves can join together to make a stable P-type orbit as well as free any nearby planets into spinning in day-night cycles?

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    $\begingroup$ "that pitting main-sequence stars in a trinary P-style orbit just isn't feasible. Such an arrangement won't allow for a stable orbit. But the smaller red dwarves don't seem to have that problem. "... so, you believe both that 1) red dwarves are NOT main sequence stars, and 2) they obey different orbital laws? I'd really like a cite on both of these factoids $\endgroup$
    – PcMan
    Dec 31 '20 at 22:31
  • $\begingroup$ If the answer was 7 it would be ironic $\endgroup$
    – L.Dutch
    Dec 31 '20 at 22:48
  • $\begingroup$ @L.Dutch-ReinstateMonica Oh? How come? $\endgroup$ Dec 31 '20 at 22:56
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    $\begingroup$ White Snow and the 7 dwarves.... $\endgroup$
    – L.Dutch
    Dec 31 '20 at 23:29
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    $\begingroup$ "How many red dwarves can join together etc.": It doesn't really matter, unless you expect the number to be in the hundreds. (And a stable gravitationally bound system with hundreds of similar sized bodies is a no-no anyway.) $\endgroup$
    – AlexP
    Dec 31 '20 at 23:59
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If you want a stable system with red dwarfs you need to take a different approach:

Put a large black hole in the center, a ring of stars around it. If the black hole is big enough your stars will be stable. The planet(s) orbit the black hole, not the dwarfs.

Do it right and you can have a habitable world, but beware of the radiation coming off the jets from the black hole--that close to the stars there certainly will be jets.

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This is a frame challenge.

You don't need a P-type orbit around a complex bunch of red dwarves to get a habitably-warm planet with day/night cycles.

An S-type orbit in a binary star system will do. The planet orbits one red dwarf, which provides most of the planet's total heat budget, and to which it is tidally locked, thus bathing one hemisphere in eternal daylight. As it completes its synchronous rotation about its primary star, however, the planet will alternately turn its other hemisphere towards and away from the second star. The light from that star will provide the day-night cycles for the antistellar hemisphere of the planet.

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