Researchers utilizing NASA’s James Webb Space Telescope have uncovered compelling evidence of an atmosphere on a rocky exoplanet, TOI-561 b, located outside our solar system. This groundbreaking discovery, published today in The Astrophysical Journal Letters, suggests that the ultra-hot super-Earth is enveloped by a dense layer of gases above a global magma ocean. The findings challenge existing beliefs about atmospheric sustainability on small planets situated close to their stars.
TOI-561 b, with a radius 1.4 times that of Earth and an orbital period of less than 11 hours, belongs to a rare category of celestial bodies known as ultra-short period exoplanets. Despite orbiting a star only slightly smaller and cooler than our Sun, the planet’s proximity—less than one million miles from its host star—implies it is tidally locked, with its dayside temperatures soaring above the melting point of typical rock formations.
Unraveling the Mysteries of TOI-561 b
Dr. Anjali Piette from the University of Birmingham remarked on the necessity of a thick, volatile-rich atmosphere to account for the observations. “Strong winds would cool the dayside by transporting heat over to the nightside,” she explained.
“Gases like water vapour would absorb some wavelengths of near-infrared light emitted by the surface before they make it all the way up through the atmosphere.”
The presence of bright silicate clouds could further cool the atmosphere by reflecting starlight.
Johanna Teske, the lead author and staff scientist at Carnegie Science Earth and Planets Laboratory, highlighted the planet’s anomalously low density.
“TOI-561 b is distinct among ultra-short period planets in that it orbits a very old, iron-poor star – twice as old as our sun – in a region of the Milky Way known as the thick disk,”
she noted. This suggests that the planet formed in a vastly different chemical environment compared to our solar system.
Exploring Atmospheric Composition
The research team hypothesized that TOI-561 b might be encased in a substantial atmosphere, which could make it appear larger than its actual size. Despite the expectation that small planets exposed to intense stellar radiation would lack atmospheres, some, like TOI-561 b, defy this assumption. Using Webb’s Near-Infrared Spectrograph (NIRSpec), scientists measured the planet’s dayside temperature by analyzing its near-infrared brightness.
If TOI-561 b were a bare rock without an atmosphere, its dayside temperature should approach 4,900 degrees Fahrenheit (2,700 degrees Celsius). However, observations revealed a temperature closer to 3,200 degrees Fahrenheit (1,800 degrees Celsius), indicating the presence of an atmosphere that redistributes heat.
Implications and Future Research
Co-author Tim Lichtenberg from the University of Groningen posited a balance between the magma ocean and the atmosphere.
“While gases are coming out of the planet to feed the atmosphere, the magma ocean is sucking them back into the interior. This planet must be much, much more volatile-rich than Earth to explain the observations.”
The concept of TOI-561 b as a “wet lava ball” presents a novel perspective on planetary formation and evolution.
These observations mark the first results from Webb’s General Observers Program 3860, which involved continuous monitoring of the system for over 37 hours. The team is now delving into the complete dataset to map the planet’s temperature distribution and refine the understanding of its atmospheric composition.
The James Webb Space Telescope, a collaborative effort between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA), continues to revolutionize our understanding of the cosmos. By exploring distant worlds and probing the universe’s enigmatic structures, Webb is poised to answer fundamental questions about our place in the universe.
