My Weekend Project

(A follow on to my nearest stars worldbuild- click here) I want to get back to world-building, but what exactly? Last night I lay hands on one of my copies of John Barnes' 'Apostrophes and Apocalyspes' with 'How To Build A Future' and he covers a lot of territory there, from specifications and background to starmaps and literal world-building. I could do something random but instead I went looking for nearby interstellar objects and the next three after Barnard's 'Flying Star' (which I did last year (see!)) are the brown dwarves Luhman 16 AB , another brown dwarf, WISE 0855-0714 (and definitely/probably not a 'star' but a rogue planet) and the infamous, among Star Trek nerds, Wolf 359 . The latter has two known planets, one of which is a super Earth, ~3.8 times the mass of Earth, with roughly four times the insolation of Earth or twice that of Venus, and the other is an ice giant about the same mass as Uranus and Neptune combined or half the mass of Saturn. Frankly, I'm interested in all three, but the brown dwarf binary probably has large worlds which could harbor life or even be terraformed. The goldilocks zone is probably inside of the roche limit for these brown dwarfs 8-(, or maybe not; Wolf 359, which is larger, hotter and presumably less dense has an estimated diameter of 110K kilometers. The objects would be very close, tidally locked and the primary would be enormous!

The brown dwarfs are about 90K km in diameter, more than jupiter but less than Wolf 359. That's roughly seven Earth diameters, which is good enough for roughing out the roche limits, so I can calculate that the brown dwarves are about 30 times as dense. Any earth-like moons would be about the same density as Earth, I'm looking at a roche limit of 2.44 times the radius times the cube root of the density of the brown dwarves over the moon (30)^1/3, or 2.44 times three and a bit, call it 7.5 radii, times 45K, or about 338K km, so, yeah, we coud have a 'moon' that close.