Multiple Habitable Worlds in A Single Star System

[Junghalli]

Is it realistic to have star systems with more than one planet bearing advanced life? So far I don't see why it would be. If Mars had come out of the oven a little differently our solar system might be one of them. Do you think it would be realistic or unrealistic to have star systems with multiple habitable worlds?

[Zed Snardbody]

wouldn't this be better suited to SLAM?

Anyway, I belive the habitable zone is large enough as to encompas the orbits of two worlds, but they wouldn't be earth like. More along the lines of really hot and really cold, but still livable.

[Zor]

If they are moons above a gas giant, yes.

Zor

[xcr]

One could be earth like, I think- Is Mars not within the zone in which it is possible for a world to be habbitable?

[Shroom Man 777]

Venus, if it turned out a bit differently a few bajillion years ago, would've been habitable. Minus the acid rain, volcanoes and other deathstuff, it's exactly just like earth exactly.

[wautd]

Venus, if it turned out a bit differently a few bajillion years ago, would've been habitable. Minus the acid rain, volcanoes and other deathstuff, it's exactly just like earth exactly.

[conspiracy mode]Hah! That's what we want you to think comrade.[/conspiracy mode]

[RedImperator]

There's no reason why there couldn't be more than one habitable planet in the same system. Dozens of them, like some people say is the case for Firefly and Battlestar Galactica, no. Not without wholesale engineering of the entire system.

[Solauren]

Sure, it's possible.

The maximum number depends on the size of the star the planets are orbiting.


For example, our own Solar System could have had 3 around the Sun (Venus, Earth, Mars), had Venus and Mars turned out a little different

A star with the size and temperature to have a large inhabitable zone around it could have any number of planets orbiting it. The closer to the sun they got, that thinner the atmosphere would have to been, and the furhter out, the thicker (to control heat trapping and so forth)

Also, in our own solar system, if Jupiter was heavier (I don't know how much heavier), it's 4 Gaileian moons are all big enough to have developed life. (I personally think the one that's frozen over, Europa is it, probably does have life on it, or did at one time)

So, it is possible.

How LIKELY it is, is another story.

[WyrdNyrd]

IIRC, you can have up to three bodies in a single, stable orbit around a fourth, e.g. three planets around a star. Or it could be just two, memory's fuzzy...

Point is, you can then double or triple the number of planets in a star's habitable zone.

[Mange]

One could be earth like, I think- Is Mars not within the zone in which it is possible for a world to be habbitable?

Both Venus and Mars is in the habitable zone. However, some scientists have started to question this rather narrow view. There could be other processes that could lead to emergence of life even in relatively remote areas of a star system.

[RedImperator]

One could be earth like, I think- Is Mars not within the zone in which it is possible for a world to be habbitable?

Both Venus and Mars is in the habitable zone. However, some scientists have started to question this rather narrow view. There could be other processes that could lead to emergence of life even in relatively remote areas of a star system.

That doesn't translate to human-habitable, though.

[GrandMasterTerwynn]

Is it realistic to have star systems with more than one planet bearing advanced life? So far I don't see why it would be. If Mars had come out of the oven a little differently our solar system might be one of them. Do you think it would be realistic or unrealistic to have star systems with multiple habitable worlds?

If you go by our solar system, you can get up to three habitable planets, depending on how the mass distribution falls out. Some solar systems will give you four or five, but that's pushing it. This assumes habitable means "large terrestrial planet like Earth." If by habitable, you mean any ball of rock capable of supporting complex life, then the total doubles, since the large moons of gas giants can have water oceans under their icy crusts.

If you include stars that have evolved off the main sequence, they have habitable zones extending from the orbit of Jupiter to past the orbit of Saturn (or, later on, past the orbit of Saturn and to the orbit of Uranus.) There, any large ice and rock moon will count as a habitable world, and you can have around ten or more.

[GrandMasterTerwynn]

Venus, if it turned out a bit differently a few bajillion years ago, would've been habitable. Minus the acid rain, volcanoes and other deathstuff, it's exactly just like earth exactly.

If Mars and Venus had been interchanged, then you'd have three habitable planets today. Far Venus would've been massive enough to hang onto a thick, pleasant atmosphere, and near Mars's low mass would've meant it would've had a harder time holding onto an atmosphere capable of producing a runaway greenhouse effect. Of course, for this to happen, you would've needed Jupiter to orbit a bit further out, which would've either meant that, instead of having the four gas giants we have now, we'd have a giant with Jupiter and Saturn's mass combined and Uranus and Neptune, a Jupiter with a less-massive Saturn, and a Uranus and Neptune, a Jupiter, a giant with Saturn and Uranus' combined mass, and a Neptune, or a Jupiter and another gas giant with Saturn, Uranus' and Neptune's mass combined, orbiting at around the orbit of Uranus.

This sort of solar system is perfectly possible, given what we know of the mechanics of solar system formation.

[Broomstick]

If you have double planets - say, if Earth's moon had been larger and more Earth-like, with an atmosphere and so forth - you could have two planets in one habitable zone. So... if venus-earth-mars orbits are "habitable", then by putting a double-planet system in each orbit you'd have six habitable worlds.

Probably not at all likely... but possible.

[xcr]

I remember a rather poor sci-fi movie in which there is another planet essentially the same as earth, in the same orbit exactly, on the other side on the sun, but I assume that is so close to impossible as to be a pointless consideration...

[Hardy]

If they wern't perfectly opposite, their gravitional interaction would also mess things up, pulling each other off stable orbits, meaning again that both planets will decay into the star.

I think that may not entirely be the case. Correct me if I'm wrong, but the leading planet would be slowed down constantly by the trailing planet's gravity, while the trailing planet will be constantly sped up. Both planets should have the eccentricity of their orbits increased, but the trailer will have its semi-major axis increased, while the lead planet should have its semi-major axis decreased. Only one planet would have its orbit "decay".

It hurts to think of what might happen in the long term, as periods and eccentricities change since the frequency and intensity of perterbations change. This is why n-body problems are not our friends.

[fgalkin]

I remember a rather poor sci-fi movie in which there is another planet essentially the same as earth, in the same orbit exactly, on the other side on the sun, but I assume that is so close to impossible as to be a pointless consideration...

You've seen Gor? I pity you.

And NOTHING about Lange's folly makes even the slightest sense (take the fact that Gor has a lighter gravity, but its inhabittants are somehow stronger than their Earth counterparts), so I fail to see why we must be discussing it.

Have a very nice day.
-fgalkin

[Junghalli]

I remember a rather poor sci-fi movie in which there is another planet essentially the same as earth, in the same orbit exactly, on the other side on the sun, but I assume that is so close to impossible as to be a pointless consideration...

If I'm not mistaken, having a second planet in the same orbit would cause both orbits to destabilize. The gravity between the two planets would add to the star's gravity, causing both them to decay into the star. If they wern't perfectly opposite, their gravitional interaction would also mess things up, pulling each other off stable orbits, meaning again that both planets will decay into the star.

Well, There are the Trojan asteroids, which move in the same orbit as Jupiter (one group moves ahead of the planet the other behind the planet). And I think there might be some smaller Jovian or Saturnian moons that share orbits but I can't remember for sure offhand.

[Hardy]

Well, There are the Trojan asteroids, which move in the same orbit as Jupiter (one group moves ahead of the planet the other behind the planet).

The Trojans are at Jupiter's L4 and L5 points where the gravity of Jupiter and the Sun balance out. Their own collective mass is too negligible to significantly perturb Jupiter, though.

And I think there might be some smaller Jovian or Saturnian moons that share orbits but I can't remember for sure offhand.

I know Metis and Adrastea satisfy this condition, but their masses are far too small to drastically perturb each other.

You can search NSSDC for such moons.
http://nssdc.gsfc.nasa.gov/
Hmm...NSSDC has a makeover.

[Mange]

One could be earth like, I think- Is Mars not within the zone in which it is possible for a world to be habbitable?

Both Venus and Mars is in the habitable zone. However, some scientists have started to question this rather narrow view. There could be other processes that could lead to emergence of life even in relatively remote areas of a star system.

That doesn't translate to human-habitable, though.

No, absolutely not (I'm sorry if I was a bit vague). It could for example be very tiny biospheres.

[Symmetry]

I remember a rather poor sci-fi movie in which there is another planet essentially the same as earth, in the same orbit exactly, on the other side on the sun, but I assume that is so close to impossible as to be a pointless consideration...

Unsuprisingly, the Wikipedia has an article on just this topic. The situation you describe (L3) would be a solution to the three body problem, but it's an unstable one and would quickly fall apart given pertubations from the other planets.

[Mange]

Space.com had an interesting article on the subject:

http://www.space.com/scienceastronomy/0 ... _like.html

[Kuja]

Imagine the budget NASA would have if Venus and Mars had turned out to be inhabitable.....

[Broomstick]

In such an instance I doubt exploration and space flight would have remained solely in government hands, or in the hands of just one agency. If there was something on either of those planets worth the trip and the risk greed would provide the impulse.

[Zaia]

To SLAM.