Habitable planets in a binary system? 2 Solar Systems next to each other?

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Offline DeaconX

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First off, hello and thank you to anyone who takes the time to look at my questions and cares to help me understand a few things.

I'm a writer and I'm currently working on something that is certainly science fiction/fantasy, but I'd still love to know if the following circumstances can occur.

Circumstance #1 : Binary star system with several (3-5) habitable worlds in the goldilocks zone.

How would these planets safely orbit the binary stars? What effects might they be susceptible to? What might life actually be like?

Circumstance #2 : 2 solar systems very close to another, practically 'touching' each other at the heliopause region.

What is the SAFEST distance between two solar systems with multiple planets in their respective goldilocks zones?

For instance, if we took our our solar system (for example) and put one much like it right on the edge of our heliopause, could the two systems exist without affecting one another for a very long period of time? Would solar winds from each star affect the other system?

I apologize if my questions are fairly absurd - it's why I'm here ;)

Thank you kindly!
« Last Edit: 22/04/2013 12:09:03 by DeaconX »


Offline yor_on

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How could anything rest if there was sunlight on 24/7? Think it would do strange things to fauna and flora myself (as a global warming effect too. Probably there would be some balance though, incoming outgoing radiation? but if it is in a equilibrium?).  And number one http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980122c.html and http://burtleburtle.net/bob/physics/binary.html for imagining :) As for the safest distance? Don't know. Depends on (types of) orbits etc.
« Last Edit: 27/04/2013 23:14:05 by yor_on »
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Offline RD

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2 solar systems very close to another, practically 'touching' each other at the heliopause region.

200AU separation is a wide binary , not "close".

The age of the binary system as well as the separation would affect the planets chance of survival ...

Quote from: nature.com
...  wide binary companions may often strongly perturb planetary systems, triggering planetary ejections and increasing the orbital eccentricities of surviving planets.

Habitable planets hoping to see a double sunset stand the best chance when orbiting twin stars that are close together.
« Last Edit: 28/04/2013 00:21:34 by RD »


Online evan_au

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Re: Circumstance #1 : Binary star system with several (3-5) habitable worlds in the goldilocks zone.
This  is fairly unlikely - planets in our solar system have orbital radii with ratios in the range 1.5-2 (counting a dwarf planet between Mars & Jupiter). This minimises orbital resonances, which are likely throw the planets out of their orbits, over time.

However, if the orbital radius is different by a factor of 1.5, the brightness of the light from their sun would differ by a ratio of (1.5)2=2.3, due to the fact that light intensity follows an "inverse square" law. Ignoring atmospheric effects, the "black-body" temperature of these two planets would also differ by a factor of 2.3 on the Kelvin scale. This is the difference in surface temperature from a balmy 300K (27C/80F) to a frigid 130K (-143C/-226F) for the next outer planet, or a sizzling 690K (416C/782F) for the next inner planet.

This ratio of brightness in our own Solar system means that Venus is a bit too hot for comfort, and Mars is a bit too cold for comfort (even ignoring little things like the runaway greenhouse effect on Venus, and a missing atmosphere on Mars).

So I guess you could fit 2 planets in the the goldilocks zone for life as we know it, if you assumed some technological help like thermal suits, underground houses or very effective air-conditioning. With 3 planets, the difference in illumination between the inner and outer of the group would be 5:1, which is a rather extreme difference in temperature, even with technological help.

I guess the plot could allow for
  • An inner planet with high-altitude reflective clouds during the day, which clear at night to allow the heat to escape (only clouds are more likely to form when temperatures cool [:(] ). A settlement near the poles would have much more bearable temperatures, especially if it were in a valley shielded from the star.
  • An outer planet could be assumed to have a thick atmosphere and greenhouse effect which increases the temperatures considerably. A settlement near the equator would be warmer, especially if there was geothermal heat.
  • This is the opposite to the way Venus-Earth-Mars is arranged.

Re: Circumstance #2 : 2 solar systems very close to another, practically 'touching' each other at the heliopause region.
Planetary orbits will remain stable provided the gravitational attraction to the nearby star is many times stronger than the gravitational attraction to its companion star.

So the inner "rocky" planets would still have fairly stable orbits if there were another star similar in size to the Sun in a circular orbit at the distance of Pluto - but without any gas giants like Jupiter to Neptune in the middle ground which could really be thrown into a chaotic orbit by being attracted to two stars at a similar distance.

This other star could easily have its own group of stably orbiting rocky planets.
« Last Edit: 28/04/2013 22:07:32 by evan_au »


Offline CliffordK

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If you had two stars separated by 200AU.
Intensity of the second star falls off by the square of the distance, or 2002 = 1/40,000 the intensity of the sun.  That would put it at about 10x the intensity of the moon, and probably not give significant warming.  A little extra nighttime light for the period of the year that the planet would be between the two stars.  No "nighttime" visibility for the period of the year when they are on the same side as the planet.

The smallest known star (brown dwarf), OTS 44 is about 15x the mass of Jupiter.  Could it exist within, say 10 AU of a sun-like star?  One slightly more massive than the sun?  The largest known super Jupiter planet, Kappa Andromedae b is about 13x the mass of Jupiter.

I don't see why one couldn't have a binary planet, somewhat like the Earth and moon, but with the second planet much larger.

Or, a larger planet such as Jupiter might be able to host Trojan and Greek planets.