The two exoplanets have been classified as a “super-Earth” and a “sub-Neptune.” This discovery was published in a paper on 15.08.2022 on arXiv.org.
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To date, NASA’s Transiting Exoplanet Survey Satellite (TESS) has confirmed over 230 exoplanets. (Illustration: MIT News)
TESS is currently conducting surveys of the brightest stars near the Sun with the goal of finding transiting exoplanets. So far, TESS has identified over 5,800 exoplanet candidates, out of which 233 planets have been confirmed.
A team of astronomers led by Faith Hawthorn from the University of Warwick, United Kingdom, has confirmed the existence of two additional exoworlds with the help of TESS. Transit signals were identified in the light curve of TOI-836 (or TIC 440887364) – a K-dwarf star located approximately 90 light-years away from Earth.
The nature of these signals was subsequently confirmed through follow-up observations using the Characterizing Exoplanet Satellite (CHEOPS) of the European Space Agency (ESA) and several ground-based observatories.
In the TOI-836 star system, the planet TOI-836 b has a radius approximately 1.7 times that of Earth and is about 4.5 times more massive, with a density of 5.02 g/cm3. This planet has an orbital period of 3.81 days around its host star, at a distance of approximately 0.0042 astronomical units (AU) – the average distance from Earth to the Sun. Its equilibrium temperature is estimated to be around 871K (597.8 degrees Celsius). With such parameters, TOI-836 b is referred to as a “super-Earth.”
“Super-Earth” refers to planets that are larger than Earth but do not exceed the mass of Neptune. While the term “super-Earth” specifically refers to the mass of the planet, astronomers also use it to describe planets larger than Earth but smaller than “sub-Neptunes” (with radii 2-4 times that of Earth).
TOI-836 c, the “sub-Neptune,” is approximately 2.6 times larger and 9.6 times more massive than our planet, resulting in a density of 3.06 g/cm3. It has an orbital period of around 8.6 days and orbits its parent star at a distance of 0.0075 AU. Its estimated equilibrium temperature is about 665K (391.8 degrees Celsius).
The host star TOI-836 is a 5.4 billion-year-old K-dwarf star, with a size and mass about 33% smaller than the Sun. Its effective temperature is around 4,552K (4,278.8 degrees Celsius).
According to the authors of the study, significant variations in transit timing during observations of TOI-836 c suggest the possibility of the existence of a non-transiting third planet in the TOI-836 star system.