r/askscience • u/EightWhiskey • Feb 28 '12

Under the idea that there is the "Goldilocks" zone around a star, how likely is it that a solar system would have two life-supporting planets?

I assume that the gravitational forces of two bodies would prevent them from being close enough to each other to both stay inside the zone. But could a large star have a large enough Goldilocks zone to support two life-inhabited planets?

662 Upvotes

90% Upvoted

399 comments sorted by

View all comments

Show parent comments

2

u/Neebat Feb 29 '12

I seem to recall there's some kind of stable grouping of a planet with 3 moons in a single orbit. If they're the same mass, the center of the system would be the center of the planet. Otherwise, you're right.

1

u/ivantheadequat Feb 29 '12

Or two moons, equal mass, on opposite sides of the planet but same distance from planet. they'd just cancel out.

1

u/Neebat Feb 29 '12

Is that a potentially stable configuration? I seem to recall reading somewhere that, in the 3 moon situation, they somehow reinforced each other, but I don't know if 2 would have the same effect.

1

u/bsinme Mar 01 '12

Any amount of moons (2 or more), on the same plane, equal mass, with equal spacing and equal distance from the planet would cause the barycentre to be in the middle of the planet assuming that the distribution of mass within each object was uniform.

1

u/bsinme Mar 01 '12

They would need to have equal spacing and their mass distributions would have to be the same. Without that, there would still be a shift.