TOI-561 b: A Rocky Planet Defying Expectations

NASA's James Webb Space Telescope (JWST) has provided groundbreaking evidence that the rocky exoplanet TOI-561 b, an ancient super-Earth located approximately 280 light-years away, possesses an atmosphere despite conditions that would typically strip such a planet of its gaseous envelope. This discovery, detailed in a study published in *The Astrophysical Journal Letters*, challenges long-held assumptions about how rocky planets retain atmospheres under extreme stellar radiation.

The Planet That Broke the Rules: Webb Telescope Finds the “Impossible” in Deep SpaceScience Daily

TOI-561 b orbits its star at a distance just one-fortieth that of Mercury from the Sun, completing a full orbit in approximately 10.56 hours. The planet's surface temperatures exceed the melting point of most rock-forming minerals, yet JWST's measurements indicate a dayside temperature of around 3,200 degrees Fahrenheit (1,800 degrees Celsius), significantly lower than the nearly 4,900 degrees Fahrenheit expected for a bare rock. This temperature discrepancy suggests that a substantial atmosphere is present, facilitating heat redistribution across the planet.

The Planet That Broke the Rules: Webb Telescope Finds the “Impossible” in Deep Space

The research team, led by Carnegie Science astronomer Johanna Teske, found that TOI-561 b's density is lower than expected for an Earth-like composition, indicating a volatile-rich atmosphere. Co-author Tim Lichtenberg described the planet as a "wet lava ball," suggesting a dynamic equilibrium between its molten interior and atmospheric gases. Gases escape from the magma ocean to form the atmosphere, while the magma simultaneously reabsorbs them, creating a continuous recycling loop.

The Planet That Broke the Rules: Webb Telescope Finds the “Impossible” in Deep SpaceScience Daily

The study also explored various atmospheric compositions, concluding that a thick, volatile-rich atmosphere is necessary to explain the observed brightness temperatures. The presence of strong winds and bright silicate clouds may further contribute to cooling the atmosphere and redistributing heat.

Science Daily

The findings regarding TOI-561 b have significant implications for the understanding of planetary atmospheres, particularly the so-called "cosmic shoreline," which traditionally predicts that planets exposed to high radiation and low escape velocities should lose their atmospheres. TOI-561 b's existence contradicts this boundary, suggesting that the mechanisms governing atmospheric retention are more complex than previously thought.

The Planet That Broke the Rules: Webb Telescope Finds the “Impossible” in Deep Space

The planet orbits an iron-poor star that is twice as old as the Sun, indicating a formation environment distinct from that of planets in our solar system. This unique chemistry may provide insights into how volatile elements are retained within a planet's interior.

The Planet That Broke the Rules: Webb Telescope Finds the “Impossible” in Deep Space

Researchers are continuing to analyze over 37 hours of JWST data to map temperature patterns and further investigate TOI-561 b's atmospheric composition. Michael Walter, Director of the Earth and Planets Laboratory, noted that the ongoing research is expected to yield more exciting results in the future, opening new avenues for understanding exoplanets.

Science Daily

The discovery of TOI-561 b stands as a testament to the complexities of planetary science, revealing that even the most extreme rocky worlds may harbor atmospheres and dynamic processes that challenge existing theories.

The Planet That Broke the Rules: Webb Telescope Finds the “Impossible” in Deep Space