Why doesn’t our solar system have sub-Neptune exoplanets and what can they teach us about planetary formation and evolution? This is what a recent study published in The Astrophysical Journal Letters hopes to address as a team of researchers investigated the atmospheric characteristics of an intriguing sun-Neptune using NASA’s most powerful space telescope. This study has the potential to help astronomers better understand the formation and evolution of exoplanets, specifically those that exhibit characteristics different from the planets of our solar system.
For the study, the researchers used NASA’s James Webb Space Telescope (JWST) to observe TOI-421 b, which is a sub-Neptune exoplanet located approximately 244 light-years from Earth and orbits inside the inner boundary of the star’s habitable zone. What makes TOI-421 b unique is that it orbits a Sun-like star and its equilibrium temperature is above that of typical sub-Neptunes, 920 Kelvin compared to approximately 500-800 Kelvin, respectively. Additionally, the researchers identified that TOI-421 b does not possess a hazy atmosphere like most sub-Neptunes, which they attribute to its atmosphere being stripped from the higher-than-normal temperatures.
“I had been waiting my entire career for Webb so that we could meaningfully characterize the atmospheres of these smaller planets,” said Dr. Eliza Kempton, who is a professor in the Department of Astronomy at the University of Maryland and a co-author on the study. “By studying their atmospheres, we’re getting a better understanding of how sub-Neptunes formed and evolved, and part of that is understanding why they don't exist in our solar system.”
This study comes as the number of NASA-confirmed exoplanets is almost 5,900, with more than 2,000 being designated as “Neptune-like” exoplanets. However, sub-Neptune exoplanets are unique in that our own solar system does not have these types of exoplanets, thus challenging our understanding of planetary formation and evolution.
What new discoveries about sub-Neptunes will researchers 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 Letters, NASA
Featured Image Credit: NASA, ESA, CSA, Dani Player (STScI)