But crossing the streams for a moment, John Varley’s Invaders were a gas giant species with a fetish for dolphins…

It wasn’t as bad as Tom Swift, or Beloved Belindy, though – try reading one of those to a child of color.  You have to either massively revise on the fly, or constantly stop to explain… “No, honey, Johnny Gruelle wasn’t a racist, it’s just that he was purposely invoking the ‘mammy’ stereotype to address an audience in a time when racism was commonplace and accepted.  Belindy isn’t stupid, she’s… what?  What does ‘invoking’ mean?  Ok, uhm…..”

It seems to me that anything with a surface temperature like that could potentially support life — both homegrown (like our own Archaea bacteria) and potentially supporting a human population deriving power and food from heat alone (though of course a potential colony would need a lot of insulation or to be build a fair distance away to prevent us from burning up…).

Right now there’s no agreed definition for planet. Contrary to what Nathan said, the IAU takes them as objects around our sun which have cleared their orbit; it doesn’t regulate exoplanets. Their definition is easy to extrapolate to other solar systems, but not free objects like this.

However, right now there’s a nice range of sizes that matches up with gaseous planets, and another that matches up with terrestrial planets plus a few moons. So “rogue planet” can fairly be taken to mean objects in that range – presumably former planets that got lost? – until we know more about them.

I suspect that the surplus of star-less planets is due to the huge supply of dirigible planets left over after the last inter-galactic war.  They were supposed to be sold off at duly authorised Army Surplus stores but they bring such low prices that I wouldn’t be surprised if unscrupulous operators have just been dumping them.