15 Jan. 2022 16:51
A recently discovered exoplanet could have liquid water on its surface, according to a recent study. The exoplanet TOI-2257b with an eccentric orbit around its home star could therefore be one of only around 20 known sub-Neptune-type planets on which suitable conditions prevail.
An international team of astronomers led by Dr. Nicole Schanche at the University of Bern has made exciting discoveries about an exoplanet orbiting a red dwarf star on an extremely elliptical, eccentric orbit. The planet, designated TOI-2257 b, was originally spotted by NASA’s Transiting Exoplanet Survey Satellite (TESS) and observed for the study over a four-month period.
The term eccentric refers here to the orbit around the home sun. Most of the known planets and moons in our solar system revolve around the sun in almost circular, only slightly elliptical orbits. In the case of exoplanets, i.e. planets outside the solar system, extremely elliptical orbits, i.e. so-called eccentric orbitals, have often been discovered. One of such exoplanets is TOI-2257 b, which orbits its host star in an unusually wide, elliptical orbit, but overall remains in a habitable zone. according to dr Nicole Schanche, this is the planet with the most eccentric orbit ever discovered near a cool star. “Red dwarfs” are small stars and much cooler than our sun. Liquid water is also possible there on planets that are much closer to the central star than in our solar system.
Shadows of the light from this solar system became visible with the TESS space telescope, which indicate the transition of a planet in front of its star. The study, recently published in the journal Astronomy & Astrophysics, also revealed its proximity to the host star, which is small and much cooler than the Sun, with a relatively short orbital period of 35 days, allowing for the existence of liquid water on its surface also a favorable prerequisite for the emergence of life as we know it and can assume it. According to the scientists, it is probably a planet of the mini-Neptune type – a small ice or gas planet.
However, the experts went on to report that the estimated radius of TOI-2257 b is 2.2 times that of our Earth, suggesting that the planet may have high atmospheric pressure, which in turn complicates potential habitability. “While the planet’s average temperature is comfortable, it varies from -80 °C to about 100 °C depending on where the planet is in its orbit, far away or close to the star,” Schanche explained, adding it it is possible that another giant planet is interfering with the orbit of TOI 2257 b and is also causing such large temperature fluctuations – in addition to the orbital eccentricity.
The study notes that the study of the exoplanet is ongoing and more observations are needed. “In particular, the planet could be examined for signs of features such as water vapor in the atmosphere,” reports Schanche, pointing to the possibility that the James Webb Space Telescope (JWST), which was launched recently in late December, will provide more insights into TOI-2257 b could bring.
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