Many planets, far from a parent star, wander the darkness of space as solitary worlds.
Cool & Creepy
Planemos are sunless worlds that do no orbit a parent star, but instead wander throughout the cosmos until captured by the gravity of a star, a larger planet, and in the case of neither, will continue to drift indefinitely through interstellar space.
Some planets, both large and small, either gas giants like Jupiter or smaller rocky worlds such as Earth, are sometimes ejected from the star system into which they were born. Any number of reasons can cause this to happen and the phenomenon is not as rare as once thought.
With the discovery of thousands of new planets orbiting parent stars, where giant worlds have spiraled inward and possess orbits very close to their suns, it surely happens that thousands, perhaps millions of other planets have departed their home solar systems for one reason or another. Still others will abandon their home galaxies entirely and travel the vast distances between the island universes.
Worth noting is the lack of external illumination that such planets would normally receive from nearby stars. Noonday on Pluto, furthest from the sun, is about the same as a dim, moonlit night on Earth. And even that is dazzling compared to the perpetual moonless midnight of a planemo. Such worlds are not, however, completely dark. At least those with some kind of atmosphere. With wind-driven, internally heated clouds. And lightning. In some cases lots of lightning. How strange might that be, from one moment to the next, to go from absolute darkness to blinding brilliance? Then back again.
Vulcanism, where geological forces generate lots of heat, some amount of light may emanate from molten rock and other super-heated fluids or gases. I can imagine no more nightmarish world (or one more beautiful) than a planemo where a visiting astronaut might be surrounded by glowing magma, phosphorescent gases and other self-florescing materials, all bombarded by endless bolts of lightning. Terms like grand and glorious likely fall far short of the true nature of such spectacles.
Strangest of all, with a beauty all their own, would be those frozen worlds without any light whatsoever, no atmosphere to speak of, no lightning, no vulcanism -- nothing but utter, absolute blackness. It’s easy to imagine asteroids and planetesimals wandering amid such bleak isolation, but an entire planet, maybe the size of Earth or larger, staggers the imagination in trying to fathom such a place. It should be noted, however, that planets which are part of a galaxy, or not that far from one, would be illuminated by the galaxy itself. In such instances, the galaxy might fill half the sky, more even, or be no larger (or brighter) than a full moon on Earth. On a clear, cloudless night, that is. And on this world, it's night every day.
The chances are good that many wandering planemos are not only interstellar, but intergalactic as well. On these planets, the nearest galaxy is little more than a pinpoint of light no bigger than a small, nighttime star. Although no word exists in English that can describe how dark such places might be, we do know that life exists in the lightless depths of the deepest oceans. And while oceanic trenches are likely still somewhat bright by comparison, one can’t help but pause and wonder. What if?