Webb Finds A Hellish Planet So Hot Its Clouds Are Made Of Rock

Recent observations from the James Webb Space Telescope have revealed that the scorching ultra-short-period (USP) exoplanet TOI-561 b unexpectedly features a highly reflective atmosphere complete with mineral-based clouds.

Located approximately 280 light-years from Earth, TOI-561 b orbits its host in less than 11 hours, close enough to keep the planet's surface in a molten lava state. Standard understanding is that a world like TOI-561 b's would have had its primordial gaseous envelope stripped away by stellar winds billions of years ago. However, Webb's NIRSpec instrument tells a different story whereby data indicates that the planet's day-side reflects heat from the G-type host star while transporting some of it to the night-side as well.

Subsequently, the existence of clouds on a world as hot and heavily irradiated as TOI-561 b is forcing scientists to rethink planetary evolution scenarios. For one, how is this gaseous layer even sustained? One hypothesis suggests that the planet may possess an ongoing replenishment mechanism, where out-gassing from the liquid rock supplies fresh volatile compounds to the upper atmosphere, balancing any ongoing atmospheric loss driven by stellar winds. Alternatively, and more simply, the planet may have started its life cycle with an exceptionally massive envelope of gases that has endured billions of years of erosion.

Currently, the researchers are trying to determine whether TOI-561 b is shrouded in a dense blanket of carbon dioxide, rather like an extreme, runaway version of Venus, or if its skies are heavily saturated with sulfur dioxide, which parallels to the volcanic venting observed on Jupiter's moon Io. Resolving these chemical mysteries will require deeper (and longer duration, since this initial observation was only for 37 hours) spectroscopic analysis at longer wavelengths.