What can sub-Neptunes, which are exoplanets whose size is between Earth and Neptune, teach astronomers about exoplanet formation and evolution? This is what a recent study accepted to The Astrophysical Journal hopes to address as a team of researchers investigated the atmosphere of TOI-270 d, which is a sub-Neptune exoplanet located approximately 73 light-years from Earth. This study has the potential to help astronomers better understand the formation and evolution of sub-Neptunes, as they remain largely mysterious with some speculating that they could be habitable.
Along with being 73 light-years from Earth, TOI-270 d is a gaseous exoplanet with a radius just over double the Earth and a mass almost five times as large. Despite its gaseous nature, TOI-270 d orbits within the inner edge of its star’s habitable zone, which is designated as an M-type star, which is both cooler and smaller than our Sun.
For the study, the researchers used a combination of data recently obtained from NASA’s James Webb Space Telescope (JWST) and computer models to better understand the atomic dynamics and composition of TOI-270 d. While JWST data revealed TOI-270 d could be a rocky world surrounded by a thick atmosphere, it also revealed temperatures exceeding 1,000 degrees Fahrenheit, which is hotter than the planet Venus. Additionally, computer models indicated that the atmospheric dynamics cause temperatures to rise to the top layers, enabling JWST to measure them. Along with the lack of habitability, the researchers concluded that TOI-270 d could contain a magma ocean beneath its atmosphere while also noting these observations are similar to planets within our own solar system.
Artist's illustration of TOI-270 d and its atmospheric properties. (Credit: Southwest Research Institute)
“While it is a bit disappointing to find that TOI-270 d is unlikely to be habitable, this planet still offers a fantastic opportunity to explore alternative paths of planetary origins and evolution,” said Dr. Christopher Glein, who is a principal scientist at the Southwest Research Institute and lead author of the study. “We are learning much more about the crazy configurations of planets that nature comes up with.”
What new discoveries about sub-Neptunes will astronomers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
Sources: The Astrophysical Journal, EurekAlert!, Southwest Research Institute