Using NASA's Transiting Exoplanet Survey Satellite (TESS), astronomers have made a groundbreaking discovery of two rocky exoplanets orbiting a nearby K-type star, known as TOI-2322. These newfound alien worlds are comparable in size to Earth and exhibit relatively short orbital periods. This significant finding was detailed in a paper published on August 25 on the arXiv pre-print server.
TESS is on a mission to survey approximately 200,000 of the brightest stars near the sun to search for transiting exoplanets. Since its launch in 2018, TESS has successfully identified over 7,600 candidate exoplanets, referred to as TESS Objects of Interest (TOI). Out of these, 686 have been confirmed so far, showcasing TESS's critical role in advancing our understanding of exoplanetary systems.
TOI-2322, also designated as TIC 300812741, is a K4 spectral type star located approximately 195 light-years away from Earth. The star has been observed multiple times by TESS between 2018 and 2023, leading to the identification of transit signals in the star's light curve. These signals suggested the presence of exoplanets, which have now been confirmed through follow-up observations led by astronomer Melissa Hobson from the University of Geneva, Switzerland.
The planets were initially identified as candidates by the TESS mission, and their characteristics were confirmed using radial velocities and activity indicators from the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO). The inner exoplanet, designated TOI-2322 b, is roughly the size of Earth, with an estimated mass of less than 2.03 Earth masses. It completes its orbit every 11.3 days, situated at a distance of about 0.09 AU from its host star, with an estimated equilibrium temperature of 603.1 K.
The second exoplanet, TOI-2322 c, is larger, with a radius of approximately 1.87 Earth radii and a mass around 18 times greater than that of Earth. This results in a density of 14.69 g/cm³. TOI-2322 c orbits at about 0.13 AU from the parent star, with an orbital period of 20.2 days and an equilibrium temperature nearing 500 K. The properties of both TOI-2322 b and TOI-2322 c suggest they are rocky short-period exoplanets.
The astronomers noted that TOI-2322 c possesses an internal structure remarkably similar to Earth, positioning it as the largest and one of the most massive planets known with an Earth-like composition. The host star, TOI-2322, is about 30% smaller and less massive than the sun, with an effective temperature of 4,664 K and a metallicity of -0.12 dex. The estimated age of TOI-2322 is around 3.9 billion years.
Additionally, the rotation period of TOI-2322 is 21.28 days, closely aligning with the orbital period of TOI-2322 c. This proximity may obscure the detection of transiting planets, making the TOI-2322 system an excellent candidate for testing methods to disentangle planetary signals from stellar activity in radial velocity measurements.
This discovery contributes significantly to the ongoing exploration of exoplanets, revealing the potential for rocky worlds beyond our solar system and enhancing our understanding of planetary formation and characteristics.
