[SPACE] Planets in a Binary Star System

[Agemegos]

Originally Posted by JediKnight83

Does this apply regardless of the planets actual distance from star B?

At any time the planet's temperature depends on it's actual distance from B at that time. (Give or take lags.)

Over long periods of time the average distance from the planet to B is equal to the [average] distance from A to B, so whswhs's method will give you a fair annual average.

[whswhs]

Originally Posted by Brett

At any time the planet's temperature depends on it's actual distance from B at that time. (Give or take lags.)

Over long periods of time the average distance from the planet to B is equal to the [average] distance from A to B, so whswhs's method will give you a fair annual average.

Exactly. I did the calculations for a binary star system for a Pyramid article a few years back, and the difference was minimal: the coldest planet was raised only from 25 K to 29 K. If the temperature boost turned out to be substantial, you could always use the minimum and maximum distances to check.

Bill Stoddard

[JediKnight83]

Sweet. Thanks guys.

[Agemegos]

If it helps, visualise the forbidden zone of a system as a disk with two circular holes cut in it. Each star is in the middle of one of the holes, and the centre of mass of the pair of stars is at the centre of the disk. The radius of each hole is one-third of the distance between the centres of the holes, and the radius of the disk is three times the distance between the centre.

In either of the holes a planet can follow a nearly-stable, almost-circular orbit around one of the stars while that star orbits the centre of mass of the system. Outside the disk a planet can follow a nearly-stable, almost-circular orbit around the centre of mass of the pair of stars for quite a long time. But in the forbidden zone things are a lot more complicated: most orbits are chaotic and end up either on a collision course or an escape course in geologically short time. The orbits that do last a long time are rather complicated and hard to deal with in Space's simple framework. (eg. Lagrange "points", horseshoe orbits, quasi-satellite orbits, etc.).

Yep, it's an approximation. But Hill Spheres are too complicated.

[JediKnight83]

Originally Posted by Brett

If it helps, visualise the forbidden zone of a system as a disk with two circular holes cut in it. Each star is in the middle of one of the holes, and the centre of mass of the pair of stars is at the centre of the disk. The radius of each hole is one-third of the distance between the centres of the holes, and the radius of the disk is three times the distance between the centre.

In either of the holes a planet can follow a nearly-stable, almost-circular orbit around one of the stars while that star orbits the centre of mass of the system. Outside the disk a planet can follow a nearly-stable, almost-circular orbit around the centre of mass of the pair of stars for quite a long time. But in the forbidden zone things are a lot more complicated: most orbits are chaotic and end up either on a collision course or an escape course in geologically short time. The orbits that do last a long time are rather complicated and hard to deal with in Space's simple framework. (eg. Lagrange "points", horseshoe orbits, quasi-satellite orbits, etc.).

Yep, it's an approximation. But Hill Spheres are too complicated.

Interesting. I never thought of it like that.