TESS reveals two rocky Earth-sized exoplanets orbiting nearby K-type star

Using NASA’s Transiting Exoplanet Survey Satellite (TESS), astronomers have discovered two rocky exoplanets orbiting a nearby K-type star, known as TOI-2322. The newfound alien worlds are comparable in size to Earth and have relatively short orbital periods. The finding was detailed in a paper published August 25 on the arXiv pre-print server.

TESS is conducting a survey of about 200,000 of the brightest stars near the sun with the aim of searching for transiting exoplanets. Since its launch into space in 2018, it has identified more than 7,600 candidate exoplanets (TESS Objects of Interest, or TOI), of which 686 have been confirmed so far.

TOI-2322, also known as TIC 300812741, is a star of spectral type K4, at a distance of some 195 light years away from Earth. The star was observed with TESS multiple times between 2018 and 2023. These observations identified transit signals in the star’s light curve, suggesting the presence of exoplanets. The planetary nature of these signals has recently been confirmed by follow-up observations conducted by a team of astronomers led by Melissa Hobson of the University of Geneva in Switzerland.

“The planets were first identified as candidates by the Transiting Exoplanet Survey Satellite mission. We confirm and characterize these planets using radial velocities and activity indicators from the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO),” the researchers wrote in the paper.

The newfound exoplanet closer to TOI-2322 received the designation TOI-2322 b. It is the size of Earth, while its mass is estimated to be less than 2.03 Earth masses. The planet orbits the host every 11.3 days, at a distance of some 0.09 AU from it, and its equilibrium temperature is estimated to be 603.1 K.

The outer, larger planet, TOI-2322 c, has a radius of approximately 1.87 Earth radii and is around 18 times more massive than Earth, which yields a density at a level of 14.69 g/cm³. The planet, located about 0.13 AU from the parent star, has an orbital period of 20.2 days and an equilibrium temperature of nearly 500 K.

The properties of TOI-2322 b and TOI-2322 c suggest that they are rocky short-period exoplanets. The astronomers noted that TOI-2322 c has an internal structure very similar to that of Earth, which makes it the largest and one of the most massive planets known with an Earth-like composition.

When it comes to the host star TOI-2322, it is about 30% smaller and less massive than the sun. The star has an effective temperature of 4,664 K and metallicity at a level of -0.12 dex. The age of TOI-2322 is estimated to be 3.9 billion years.

The authors of the paper noted that the rotation period of TOI-2322 is 21.28 days, which is therefore close to the orbital period of TOI-2322 c, which may mask the presence of a transiting planet. Due to this, the TOI-2322 system is an excellent place to test methods of disentangling planetary and activity signals in radial velocity measurements.

© 2025 Science X Network