A super-Earth located approximately 280 light-years away is defying expectations by maintaining an atmosphere despite surface temperatures exceeding 3,000 degrees Fahrenheit. The exoplanet, known as TOI-561 b, orbits its star so closely that it completes a full revolution every 11 hours. Originally discovered in 2020 by NASA's TESS spacecraft, the planet was previously thought to be too hot to possess any atmospheric layer.
However, after analyzing 37 hours of data covering nearly four full orbits with the James Webb Space Telescope (JWST), scientists have identified a reflective layer of vaporized silicate mineral clouds surrounding the world. These compounds belong to the same family as quartz and sand. Lisa Dang of the University of Waterloo explained that phase curve measurements showed the planet reflects significant starlight and redistributes heat, confirming the presence of an atmosphere.
TOI-561 b is tidally locked, meaning one side permanently faces its star while the other remains in perpetual darkness. Researchers noted that the dayside appeared cooler than expected for bare rock, suggesting either heat redistribution to the nightside or reflection away from the surface. Observations of the nightside revealed it was not warm enough to account for all the missing heat from the dayside, indicating that the planet reflects roughly three-quarters of incoming starlight.
This high reflectivity is comparable to Venus, which reflects about 75% of sunlight, far exceeding Earth's 30%. The team determined that clouds composed of silicon dioxide and magnesium silicate form on the dayside, acting like sunscreen and potentially helping the planet retain its atmosphere. While the exact composition remains uncertain, it could resemble a dense carbon dioxide fog similar to Venus or a sulfur dioxide blanket akin to Jupiter's moon Io, possibly replenished by volcanic activity.
Future observations at longer wavelengths with JWST aim to determine whether TOI-561 b's atmosphere is more like Venus or an extreme version of Io. These studies will help explain how such a scorching planet has managed to hold onto an atmosphere for billions of years. The findings were published in The Astronomical Journal.
Sources: Space.com.