View Full Version : Habitable zones in close K5V binaries

2009-Jan-30, 10:53 PM
Hi, I need to know some things about the subject. I'm doing an add-on for Celestia called Solarius and I want to make it with "realism". I'm doing an alternate version of our solar system, in which the inner planets orbit a giant called Zeus and many other changes.

But the most important thing is: The system is a trinary system with 2 close K5V stars, called Solaris and Solanus and a third star called Cronos that is a L5V star (Cronos is Jupiter, but being a brown dwarf). Both K5V stars orbit each other at a distance of 0.05 AU (7500000 Km) and Cronos orbit the pair at distance of 150 AU (22500000000 Km).

What I want to know is: considering Earth, what would be the size of the habitable zone with a pair of stars that orbit each other at 0.05 AU, both having surface temperature of 4350 K and having diameter of 475000 Km? I put Tiamat (Earth) at a distance of 4 AU (600000000 Km), almost as distant as Jupiter to Sun. I put at this distance because both stars, orbiting at certain distance will turn the star zone hotter, expanding the habitable zone.

When I say the size of habitable zone, I mean the distance of inner and outer limits of the zone. I think that, in our system, the inner limit is 0.75 AU and the outer limit around 1.5 AU. But in the case of Solarius distance, with all the factors I mencioned, I think would have 4x values. So, in Solarius, the inner limit is 3 AU and the outer limit is 6 AU. Pretty good space for many Earth-like worlds in a same system!

So with this I think that close pairs of stars (but not so close!) with bigger and denser planetary disks will increase the chances for the formation of multiple Earth-like planets per system. And a planet that orbit a pair of close stars won't have the problem of tidal-locked rotations if it orbits close. In the case of Solarius system, there are many Earth-like moons orbiting 2 gas giants, Zeus and Poseidon.

I want to know this because I think that a close pair of stars would form a bigger planetary disk, allowing much more planets to form. This is why I'm making Solarius, a better version of our Solar System.

2009-Jan-30, 11:23 PM
You should learn some elementary astrophysics before attempting such an elaborate fantasy.

grant hutchison
2009-Jan-30, 11:58 PM
A K5 dwarf has has about 0.15 times the luminosity of the sun. Two of them will average about 0.3 times the luminosity of the sun. Your habitable zone is therefore smaller by a factor of sqrt(0.3).

Grant Hutchison

2009-Jan-31, 12:29 PM
I forgot to say that these Earth-like moons have higher concentrations of greenhouse gases, some of them have higher air pressure and that colder worlds of this type have oceans of water-ammonia (colder worlds have even more greenhouse gases kept by volcanism caused by tidal heating due to gas giant), so this will expand the habitable zone at least 2 or 3 times. Because of this I expanded the size of habitable zone 3x (from 0.45AU to 1.35AU).

I want to know if what I said is true.

2009-Jan-31, 02:23 PM
One more thing. It's about the distance between 3 worlds. Lucifer has mass similar to Neptune and orbit the pair at distance of 0.25AU. Zeus has 5 Jupiter masses and orbit the pair at 1AU distance. Poseidon has 1.5 Jupiter masses and orbit at a distance of 3AU. I want to know if these worlds would be in a stable orbit.

Note: I changed the distance between Solaris and Solanus from 0.05AU to 0.02AU.

Looks like that Solarius system is a mixture of 55 Cancri with our Sol system!