Scientists Uncover Atmosphere on 1,800°C Exoplanet TOI-561 b

Researchers have made a groundbreaking discovery regarding the exoplanet TOI-561 b, located approximately 280 light years from Earth. A team of scientists using NASA’s James Webb Space Telescope has detected significant evidence of an atmosphere surrounding this ultra-hot super-Earth, characterized by daytime temperatures soaring to 1,800°C. This finding challenges the established belief that small rocky planets so close to their stars cannot retain atmospheres.

Challenging Existing Theories

Lead author Johanna Teske from the Carnegie Science Earth and Planets Laboratory explained that the planet’s surprisingly low density sets it apart from other known celestial bodies. She noted, “It is less dense than you would expect if it had an Earth-like composition.” This unique density is particularly intriguing as TOI-561 b orbits an ancient, iron-poor star that is approximately twice as old as our Sun, situated in the thick disk region of the Milky Way.

With a radius about 1.4 times that of Earth, TOI-561 b belongs to a rare category known as ultra-short period exoplanets. It orbits its host star at a distance of less than 1 million miles, significantly closer than the distance between Mercury and the Sun. This close proximity raises questions about how such a planet could maintain an atmosphere, as previous models suggested that high temperatures would strip away any gaseous envelope.

Innovative Research Methods

The research team employed the Near-Infrared Spectrograph (NIRSpec) on the James Webb Telescope to analyze the planet’s dayside temperature by measuring its near-infrared brightness. The method involved observing the light decrease as TOI-561 b passed behind its star, a technique previously used in studies of other rocky worlds, including the TRAPPIST-1 system.

If TOI-561 b were merely a bare rock, its dayside temperature would be expected to approach 2,700°C. Instead, NIRSpec observations indicated a temperature around 1,800°C. This significant finding suggests that a considerable heat transfer mechanism is at work, leading scientists to consider that a thick atmosphere, rich in volatile compounds, could be responsible for the observed temperature.

Co-author Dr. Anjali Piette from the University of Birmingham emphasized the necessity of a substantial atmosphere to account for all observations. “We really need a thick volatile-rich atmosphere to explain all the observations,” she stated. The presence of strong winds could facilitate heat transportation from the dayside to the nightside, thereby affecting temperature readings.

Additionally, researchers speculate that gases, including water vapour, could absorb certain wavelengths of near-infrared light, making the planet appear cooler than it actually is. The potential for bright silicate clouds reflecting starlight could also contribute to this cooling effect.

Insights into Planet Formation

The findings raise intriguing questions regarding the planet’s composition. One hypothesis suggests that TOI-561 b may have a smaller iron core with a less dense mantle, differing from Earth’s structure. Despite the compelling evidence for an atmosphere, a critical question remains: how can a small planet exposed to such intense radiation sustain a substantial atmosphere?

Co-author Tim Lichtenberg from the University of Groningen posited that there may be a delicate balance between the magma ocean on the planet’s surface and its atmosphere. “While gases are coming out of the planet to feed the atmosphere, the magma ocean is sucking them back into the interior,” he explained. He further suggested that TOI-561 b must possess a higher concentration of volatile elements than Earth to justify the observations, describing it as “really like a wet lava ball.”

The research findings will be published in The Astrophysical Journal Letters, contributing to the ongoing exploration of planetary atmospheres and their formation. The James Webb Space Telescope, recognized as the world’s leading space science observatory, continues to uncover mysteries across our solar system and beyond, probing the origins of the universe and the characteristics of distant worlds.