TOI-561 b is twice the mass of Earth, orbits its star every 10.56 hours at one-fortieth the distance of Mercury from the Sun, and should have lost any atmosphere billions of years ago. The star is twice the age of the Sun. The planet's surface temperature should be nearly 2,700 degrees Celsius. At that proximity and that age, stellar radiation and extreme heating should have stripped every volatile molecule long ago.
The James Webb Space Telescope measured a dayside temperature of 1,800 degrees Celsius — nine hundred degrees cooler than the bare-rock prediction. The deficit is diagnostic: heat is being redistributed from the dayside to the nightside, which requires an atmosphere thick enough to circulate. A bare rock can't move heat. A blanketed rock can.
The planet shouldn't have this atmosphere. It's too small — rocky planets at ultra-short periods are supposed to lose their atmospheres within the first few hundred million years. It's too hot — at these temperatures, most volatile species dissociate or escape. It's too old — the star belongs to the Milky Way's thick disk, an ancient, iron-poor population that formed early in the galaxy's history. Everything about the system says the atmosphere should be gone.
Two possible explanations: the atmosphere is continuously replenished by volcanic outgassing from a magma ocean surface, or the atmosphere's composition is dominated by species that are unexpectedly resistant to escape at these conditions. Either way, the conventional model — that ultra-short-period rocky planets are bare — is wrong for at least this case.
The planet is a survivor. Whatever process is maintaining the atmosphere has been doing so for ten billion years, against conditions that should have stripped it in a fraction of that time. The blanket that shouldn't exist is still there.