07/30/2026
This planet has no sun. It never had one for long, and it will never have one again.
Rogue planets β the formal term is free-floating planetary-mass objects β are worlds that
formed inside a solar system and were then thrown out of it. Planetary systems are chaotic
places while they are assembling. Young planets migrate, tug on each other, and occasionally one
gets a gravitational slingshot violent enough to exceed the star's escape velocity. It leaves.
There is no mechanism to bring it back.
Current estimates suggest there may be more of these than there are stars in the galaxy. A
microlensing survey published in 2023 put the population of Earth-mass rogues at roughly twenty
for every star in the Milky Way. If that figure holds, sunless worlds are not an exotic edge
case. They are the most common kind of planet there is, and we simply cannot see them, because
a planet with no star to illuminate it emits almost nothing.
The surface conditions are close to the coldest possible. With no stellar input, temperature is
governed by residual formation heat and radioactive decay in the interior, and the exterior
settles toward the temperature of deep space itself, around 3 kelvin above absolute zero.
Atmospheres freeze out entirely and fall to the ground as ice.
The sky, however, is extraordinary. There is no sun to wash it out, no daylight cycle, and no
seasons β the darkness is permanent and total. Every star visible from that surface is visible
all of the time. It is, without competition, the best view of the galaxy available anywhere.
And there is one further possibility that keeps this from being purely bleak. A rogue planet
with a thick enough hydrogen atmosphere, or a sufficiently hot interior, could plausibly
maintain liquid water beneath an ice shell using its own internal heat alone. No sunlight
required. If life can begin in that kind of environment β and we genuinely do not know whether
it can β then most of the habitable real estate in the universe is drifting alone in the dark,
under a sky like this one, with nobody to look up at it.