Scientists have recently found strong evidence for a rocky planet beyond our solar system that has an atmosphere. This challenges the idea that small, close-orbiting planets can’t hold onto thick gases.
Meet TOI-561 b, a super-Earth located about 280 light-years away. It orbits a 10-billion-year-old star and is believed to have a vast ocean of molten rock. Researchers used NASA’s Webb Space Telescope to explore this ultra-hot planet. They discovered signs of a thick atmosphere, which helps explain why TOI-561 b has a surprisingly low density. Understanding these rocky worlds is crucial for better grasping our universe.
Discovered in 2020, TOI-561 b is the innermost of at least three planets circling a G-type star. Although its star is a bit smaller and cooler than our Sun, TOI-561 b orbits much closer, just a million miles away. Because of this, one side of the planet likely always faces the star.
Johanna Teske, a scientist from Carnegie Science Earth and Planets Laboratory, noted that the planet’s low density sets it apart from typical rocky worlds. “It’s not a super-puff, but it is less dense than you would expect if it had an Earth-like composition,” she explained.
You might think that with such close proximity to its star, TOI-561 b would be too hot to retain an atmosphere. The intense radiation could make atmospheric gases escape into space. Yet, its low density suggests that it isn’t just a rocky body.
To dig deeper, researchers examined TOI-561 b’s dayside temperature using Webb’s Near-Infrared Spectrograph. If the planet lacked an atmosphere, temperatures on the star-facing side would rise to nearly 4,900°F (2,700°C). However, Webb’s observations revealed a temperature closer to 3,200°F (1,800°C). This discrepancy hints that some atmosphere must exist to account for the cooler temperature.
The team considered other explanations but found none to be as convincing. Without an atmosphere, the planet’s nightside would likely be solid, hindering heat transfer. The magma ocean could contribute slightly, but not enough to explain the temperatures observed. Anjali Piette, a researcher at the University of Birmingham, stated, “We really need a thick volatile-rich atmosphere to explain all the observations.”
The real mystery lies in how such a small planet can maintain a thick atmosphere despite heavy radiation. The researchers suggest this might come from a balance with the magma ocean. Tim Lichtenberg from the University of Groningen 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 added that TOI-561 b is likely much more volatile-rich than Earth.
This discovery opens doors for understanding rocky exoplanets and their atmospheres. Research like this sheds light on the complexities of our universe and challenges our assumptions about what these distant worlds can be like. As we explore further, who knows what else we might uncover?
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