A team of scientists has discovered significant evidence of a rocky exoplanet with an atmosphere, challenging long-held beliefs about small planets orbiting closely to their stars. The planet, known as TOI-561 b, orbits a star approximately 280 light-years from Earth, providing new insights into how these celestial bodies can maintain thick atmospheres despite their extreme conditions.
Research conducted using NASA‘s Webb Space Telescope revealed that TOI-561 b, a super-Earth with a vast magma ocean, possesses a thick atmosphere. This finding contradicts the prevailing notion that planets in such close proximity to their stars cannot sustain substantial gas layers.
Unprecedented Discoveries in Exoplanet Research
TOI-561 b was initially discovered in 2020 and is the innermost of at least three planets orbiting an ancient G-type star that is around 10 billion years old. The planet orbits its star at a distance of less than one million miles, leading to the expectation that it would be tidally locked and experience extreme temperatures. Its orbital period is remarkably short, completing a rotation every 11 hours.
Johanna Teske, a staff scientist at Carnegie Science Earth and Planets Laboratory and lead author of a study published in The Astrophysical Journal Letters, highlighted the planet’s “anomalously low density.” While it does not qualify as a “super-puff,” its density is lower than would be expected for a planet with an Earth-like composition.
The close proximity to its host star results in scorching temperatures that would typically prevent the retention of an atmosphere. The intense radiation emitted by the star could cause atmospheric gases to escape into space. Yet, the low density of TOI-561 b suggests it is not composed solely of rock or lava.
Investigating the Planet’s Atmospheric Dynamics
The research team, aiming to discern whether TOI-561 b is primarily a rocky body or if there are other factors at play, utilized the Webb Space Telescope’s NIRSpec (Near-Infrared Spectrograph) to determine the temperature of the planet’s dayside. Without an atmosphere to distribute heat, temperatures on the star-facing side should reach approximately 4,900 degrees Fahrenheit (2,700 degrees Celsius). However, Webb’s observations indicated a temperature closer to 3,200 degrees Fahrenheit (1,800 degrees Celsius), suggesting the presence of an atmosphere.
Exploring alternative explanations for these findings, the researchers found that without an atmosphere, the nightside of the planet would likely be solid, which would hinder heat transfer. While the planet’s magma ocean could potentially contribute to a thin layer of rock vapor, this effect would be minimal.
Anjali Piette, a researcher at the University of Birmingham, emphasized the need for a “thick volatile-rich atmosphere” to account for the observations made. The presence of an atmosphere on TOI-561 b appears to be the most plausible explanation, raising questions about how such a small planet can maintain a dense gas layer when subjected to substantial radiation from its star.
Tim Lichtenberg, a researcher at the University of Groningen, proposed that an equilibrium exists between the magma ocean and the atmosphere. He explained, “At the same time that gases are coming out of the planet to feed the atmosphere, the magma ocean is sucking them back into the interior.” He concluded that TOI-561 b must be “much, much more volatile-rich than Earth” to explain the observations, describing it as a “wet lava ball.”
These revelations not only provide new insights into TOI-561 b but also enhance our understanding of rocky worlds beyond the solar system. As researchers continue to analyze this intriguing exoplanet, they may uncover more about the complex dynamics between magma oceans and atmospheric retention, potentially reshaping our knowledge of planetary formations and atmospheres in the universe.
