Revolutionary Discovery: Ultra-hot Exoplanet TOI-561 b Retains Atmosphere Against the Odds

In a groundbreaking discovery that challenges conventional astrophysical theories, a team of astronomers led by Carnegie scientists has revealed the strongest evidence yet of an atmosphere surrounding a rocky exoplanet. This discovery, detailed in The Astrophysical Journal Letters, uncovers an unexpected atmosphere on the ancient, ultra-hot super-Earth known as TOI-561 b. This planet, likely hosting a global magma ocean, resides beyond our solar system and is roughly twice the mass of Earth.

TOI-561 b orbits its host star at a remarkably close proximity, completing a full revolution in just over 10 hours. Traditionally, such proximity, coupled with intense stellar radiation, would be expected to strip a planet of its atmosphere entirely. However, observations by NASA’s James Webb Space Telescope (JWST) have revealed that TOI-561 b defies these expectations. The planet is swathed in a dense atmosphere rich in volatile compounds, including water vapor, oxygen, and carbon dioxide. This finding poses a significant challenge to current models of atmospheric dynamics for ultra-short-period planets.

Nicole Wallack, a postdoctoral fellow at Carnegie Science, highlights the significance of the discovery: “The presence of this surprisingly resilient atmosphere contradicts the conventional assumption that smaller, hotter planets lose their gaseous blankets shortly after they form.” The Carnegie team utilized JWST’s Near-Infrared Spectrograph (NIRSpec) to analyze the planet’s dayside temperature. They discovered it was much cooler than expected for an exposed, rocky planet. This indicates that atmospheric winds are redistributing heat across the planet, a process suggesting a dynamic and substantial atmospheric layer.

Among the intriguing theories proposed by the research team is the idea of a continuous gas exchange between the magma ocean and the atmospheric shell. This equilibrium could enable TOI-561 b to maintain its thick atmosphere despite significant external radiation pressure.

Johanna Teske, also of Carnegie Science, notes, “This new dataset is opening up even more questions than it’s answering.” The study not only expands our understanding of how planets form and maintain atmospheres but also underscores the complexity and diversity of planets in the universe.

Key Takeaways:

• TOI-561 b is an ultra-hot super-Earth that unexpectedly retains a thick atmosphere despite its close proximity to a host star and intense radiation.
• Data from NASA’s JWST indicated a cooler-than-expected dayside temperature, pointing to effective atmospheric heat distribution.
• The atmosphere, enriched with volatiles such as water vapor, defies traditional models of atmospheric retention under extreme conditions.
• Ongoing research will continue to explore the planet’s atmospheric dynamics, providing new insights into planetary evolution and the variety of galactic environments.