Naked Super-Earth Planets That Orbit Their Stars in 24 Hours Discovered by Scientists

Astronomers have found that two recently discovered "super-Earths" outside the solar system lack atmospheres, uncovering the fact that one of these worlds is one of the most massive super-Earths discovered to date.

The extrasolar planets, or exoplanets, orbit their red dwarf parent stars in extremely close proximity, meaning that they complete an orbit within 24 hours. The worlds offer astronomers a unique opportunity to investigate how atmospheres form around rocky, or terrestrial, planets like Earth.

TOI-1634b and TOI-1685b both orbit different red dwarf stars and are located 115 and 123 light-years away from Earth respectively. The exoplanets were both discovered in 2021 by NASA's Transiting Exoplanet Survey Satellite (TESS).

A group of astronomers from the Astrobiology Center, the National Astronomical Observatory of Japan, the University of Tokyo, and other institutes used Subaru Telescope and several other telescopes to conduct follow-up investigations on the exoplanets. The team discovered that not only do they lack atmospheres, but they also orbit their home star in periods of under 24 hours.

That means a year on these two worlds lasts less than a day here on Earth. The team's research is documented in a paper published in The Astronomical Journal.

The exoplanets TOI-1634b and TOI-1685b are both classified as super-Earths meaning that while they are both rocky worlds like our planet, they are considerably larger.

The new research shows that TOI-1634b is the most massive super-Earth with an ultrashort orbit that astronomers have found to date. It has 10 times the mass of Earth with a radius nearly twice as big as that of our planet. TOI-1685b is slightly less massive with almost four times our planet's mass also with 1.5 times Earth's radius.

The exoplanets' close proximity to their host red-dwarf stars could be the reason that they lack the thick hydrogen-helium atmospheres possessed by many terrestrial planets. That doesn't mean these planets are completely naked, however.

The exoplanets have a thin secondary atmosphere made up of gases released from inside the planet. That means they give astronomers a unique opportunity to investigate how atmospheres develop on rocky worlds, especially those that dwell close to their parent stars.

"Our project to intensively follow-up planetary candidates identified by TESS with the Subaru Telescope is still in progress, and many unusual planets will be confirmed in the next few years," Astrobiology Center of the National Institute of Natural Sciences assistant professor, and lead author of the research, Dr. Teruyuki Hirano, said in a press release from the National Astronomical Observatory of Japan.

TOI-1634b, Earth, and TOI-1685b
TOI-1634b and TOI-1685b as they appear in NASA's exoplanet catalog. Astronomers have discovered that these super-Earths are considerably larger than our planet. NASA