An international research team led by the University of Bern has discovered a new exoplanet smaller than Neptune (“sub-Neptune”) orbiting around a red dwarf star, the University said on Friday.

This exoplanet, a planet that orbits a star outside our solar system, has been baptised TOI-2257 b and has a particularly unusual orbit, according to a press releaseExternal link on Friday.

It was discovered using the so-called transit method. This involves using telescopes to look for dips in the star's brightness when the planet passes in front of it, allowing researchers to determine the planet’s orbit and diameter.

“With its 35-day orbital period, TOI-2257 b orbits the host star at a distance where liquid water is possible on the planet, and therefore conditions favourable for the emergence of life could exist,” says the University of Bern. But its radius (2.2 times larger than Earth’s) “suggests that the planet is rather gaseous, with high atmospheric pressure not conducive to life”. 

“We found that TOI-2257 b does not have a circular, concentric orbit,” explains Nicole Schanche of Bern University, who led the research published in the scientific review Astronomy & Astrophysics. In fact, it is the most eccentric planet orbiting a cool star ever discovered. “In terms of potential habitability, this is bad news,” Schanche continues. “While the planet's average temperature is comfortable, it varies from -80°C to about 100°C depending on where in its orbit the planet is, far from or close to the star.”

A possible explanation for this surprising orbit is that a giant planet could be lurking further out in the system and disturbing the orbit of TOI 2257 b, says the press release. It adds that further observations are needed, and that this exoplanet could be a candidate for observation by the James Webb Space Telescope (JWST) launched on December 25, which “will revolutionize research into exoplanet atmospheres”.

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