Several months ago I read a story, probably on the Yahoo news, about a planet that doesn’t orbit any sun. It’s just out there, moving through the darkness of outer space all by itself. They’ve termed it an “orphan” planet. That’s a good term. It must be lonely out there. No sun, no light whatsoever, except from the stars, and that’s not much. No radiation striking its surface to power the development of life forms. No one seemed to know where it came from, or where it’s going. It’s just an orphan, doomed by fate and the fickle bonds of gravity to explore the galaxy all by itself. The philosophical implications are considerable.
It had to come from somewhere, though. Almost certainly it was born circling a star. It probably condensed out of the dust and gas that surrounds new stars as they themselves are born. But somehow it got ejected from an orbit around the star and was thrown into the void to wander around, a menace to celestial navigation. At least by those civilizations capable of navigating the galaxy. Star Trek anyone?
There is a theory among some astronomers that our solar system originally had three large gas giant planets approximately the size of Jupiter and Saturn, and the third one, in the early stages of the solar system, got ejected in a sort of planetary power struggle and is no longer with us. The theory says that Jupiter and Saturn were opposite in position from where they are now, that is, Saturn was closer to the sun. But in the re-alignment of the planets as the solar system matured, and as Saturn and Jupiter switched places, the third gas giant was kicked out. Whether or not the planet that was spotted by astronomers is that planet I can’t say. Probably not. There may be many such “orphan” or “rogue” planets out there. If we, in our infant ability to spot extrasolar planets, can spot one orphan, that suggests many more may exist.
As for life on that planet, it’s doubtful. That planet must be awfully cold. It may have a hot interior, as Jupiter does, but its surface may be frigid. I find myself wondering if it, or another one like it, might find its way into our solar system and collide with a planet of ours. Even Earth. That would make an interesting science-fiction story. We could see it coming long before it collided with us. There would be a tremendous scramble to leave Earth in whatever type of spacecraft we could find or make. If we had explorers on Mars (to postulate one scenario) they might be forced to watch as the two planets collided and their home destroyed in a huge explosion. No more supplies from Earth, folks, you’re on your own. A huge planet two or three times the size of Jupiter would probably engulf the Earth and continue on its way without much visible change. Perhaps it might even go into orbit around the sun in a sort of astronomical game of bait and switch. Perhaps I should say, “engulf and switch.”
On the other hand, suppose the orphan planet is a hard, rocky planet, the size of Uranus or Neptune. The surface might also be cold, but perhaps an intelligent civilization could have survived by living deep below the surface. They could gain heat from the interior and make electricity to power all sorts of gadgets, including life support systems. An interesting possibility. Maybe I’ll do something with that story line in the near future. Before it collides with Earth.