June 8 (UPI) – Astronomers have discovered a temperate, sub-Neptune-sized exoplanet orbiting a nearby M dwarf star.
Preliminary observations of the Earth-like planet, described Wednesday in the Astronomical Journal, suggest that the alien world may boast a significant atmosphere – which will certainly inspire follow-up studies in the coming years.
The exoplanet, TOI-1231 b, was originally seen using photometric data from the Transiting Exoplanet Survey Satellite or TESS.
Follow-up observations captured using the Planet Finder Spectrograph on the Magellan Clay Telescope at the Las Campanas Observatory in Chile allowed scientists to determine the planet̵
TESS trains its gaze on parts of the night sky for almost a month at a time, taking pictures of thousands of stars.
Astronomers, citizen scientists and algorithms scan the data for the attenuation of exoplanets as they orbit their host stars.
Because M dwarf stars are smaller and weaker than stars like the Sun, the transits of nearby stars have a more pronounced attenuation effect.
Still, astronomers were lucky that TESS took the presence of TOI-1231 b, which takes 24 days to complete an orbit around the host star.
To confirm the presence of an exoplanet, TESS typically needs to capture two passages or the completion of a orbit.
Since TESS only stares at a section of the sky for 28 days, the average orbital period of exoplanets spotted by TESS is 14 days.
Researchers said TESS caught the TOI-1231 b at the right time.
“We worked with a group of excellent astronomers spread across the globe and were able to gather the data needed to characterize the host star and measure both the planet’s radius and mass,” said research author Jennifer Burt in a press release.
“These values again allowed us to calculate the planet’s density and hypotheses about what the planet is made of. The TOI-1231 b is largely similar in size and density to Neptune, so we think it has a similarly large, gaseous atmosphere,” Burt said. , a scientist at NASA’s Jet Propulsion Laboratory.
In addition to enabling a more robust exoplanet transit signal, the small stature of an M dwarf star also makes it easier for astronomers to calculate the masses of newly discovered exoplanets, as the ratio of planet to star mass is greater.
Astronomers calculate an exoplanet’s mass by measuring the planet’s light gravity on its host star – the smaller the star, the greater the gravitational effect of an exoplanet.
“Although the TOI-1231 b is eight times closer to its star than the Earth’s to the sun, its temperature is similar to that of the Earth, thanks to its cooler and less bright host star,” said study author Diana Dragomir in the release.
“But the planet itself is actually larger than Earth and slightly smaller than Neptune – we can call it a sub-Neptune,” said Dragomir, an assistant professor of astronomy at the University of New Mexico.
What astronomers have been most excited about in the TOI-1231 b is its atmosphere.
Previous studies suggest that small, cool planets similar to the newly discovered exoplanet are capable of holding water in the upper layers of their atmosphere.
“The low density of TOI-1231 b indicates that it is surrounded by a significant atmosphere rather than being a rocky planet. But the composition and extent of this atmosphere is unknown!” said Dragomir.
“TOI-1231 b could have a large hydrogen or hydrogen helium atmosphere or a denser water vapor atmosphere. Each of these would point to a different origin so astronomers could understand if and how planets form differently around M dwarfs compared to planets around our sun, for example, ”Dragomir said.
The scientists said they hope future observations will help them work on the exoplanet’s atmospheric composition as well as determine how rare or common such exoplanets are.