A multinational team of researchers led by experts from NASA's Jet Propulsion Laboratory and The University of New Mexico identified a new, temperate sub-Neptune-sized exoplanet with a 24-day orbital period circling a nearby M dwarf star. Because of the planet's thick atmosphere, small star, and how quickly the system is travelling away from Earth, the recent discovery provides fascinating research options, according to researchers.
Called TOI-1231 b, the exoplanet was discovered using photometric data from the Transiting Exoplanet Survey Satellite (TESS) and confirmed with observations made with the Planet Finder Spectrograph (PFS) on the Magellan Clay telescope at Chile's Las Campanas Observatory.
The PFS is advanced equipment that identifies exoplanets by measuring their gravitational pull on their home stars. The observed stellar velocities vary periodically as the planets orbit their hosts, indicating the presence of the planets as well as information about their mass and orbit.
"Working with a group of excellent astronomers spread across the globe, we were able to assemble the data necessary to characterize the host star and measure both the radius and mass of the planet," said Jennifer Burt, the lead author of the paper. "Those values in turn allowed us to calculate the planet's bulk density and hypothesize about what the planet is made out of. TOI-1231 b is pretty similar in size and density to Neptune, so we think it has a similarly large, gaseous atmosphere."
TOI-1231b is one of the coolest, tiny exoplanets identified thus far, with a temperature of roughly 330 Kelvin or 140 degrees Fahrenheit. Previous study indicates that planets this frigid may have clouds high in their atmospheres, making it difficult to tell what kind of gases surrounds them. However, new investigations of another small, chilly planet known as K2-18 b defied this pattern and revealed evidence of water in its atmosphere, stunning many scientists.
Another method for studying the planet's atmosphere is to look for signs of atoms like hydrogen and helium around the planet when it transits over the face of its host star. In general, hydrogen atoms are difficult to detect because their presence is obscured by interstellar gas. However, owing to how quickly it is travelling away from the Earth, this planet-star system provides a unique opportunity to apply this strategy.
