Damon wrote:I recommend Helliconian planets as the name
That was my first thought too.
Yerushalmi wrote:I guess an intrabinary planet would be one where the suns pull on the planet equally so it doesn't move at all?
binary" seems to fit that situation, as the planet would always be between
the two stars. (It doesn't exist of course, as it would be unstable.)
EngrBohn wrote:I suggest that "the other type" be called a Nightfall binary, after Asimov's story.
Lagash, the planet in Nightfall
, has no less than six suns, so there should be plenty of chances to see rainbows.
speising wrote:I assume the "3" as radius in the picture should be "6".
Then his angle is wrong, too, since tan-1
(0.5/3)x2 = 18.9o
. (Calling that "about 18" is a bit odd, too, but unimportant given that we only care if it's greater or less than 84.)
Maybe the pic is correct and the previous text is wrong?
In the article that note 7 links to
, the relevant results seem to be in table 7 on page 11. The numbers are described as "the critical semimajor axis in units of the binary semimajor axis", and range from 2.0 to 4.2. When the orbits are close enough to circular we can read "semimajor axis" as "radius". A mass ratio µ
of 0.5 means that the suns have equal masses. For the easiest case, circular orbits (e
= 0.0) and equal masses (µ
= 0.5), the planet's critical distance from the center of the system (critical semimajor axis) is 2.3 times the suns' distance from the center of the system (binary semimajor axis) – not the suns' distance from each other. That means an angle of tan-1
(1/2.3)·2 ≈ 47°.
Note also that in the article an orbit is considered stable if the planet survives for just a few thousand years, and there are regions further out that are unstable due to resonance. I find it doubtful that a planet can survive that close to a binary star long enough for beings who can look at rainbows to evolve.