TOI-2257b is the most eccentric subneptunic exoplanet ever discovered

TOI-2257b is the most eccentric subneptunic exoplanet ever discovered

Detected with the help of TESS, it is the most eccentric planets around a red dwarf star, and its temperature suggests the presence of liquid water: the clouds of its atmosphere can be seen from James Webb's space telescope.

One of the most successful methods of detecting an exoplanet is known as a transit technique. In our galaxy, more than 2,000 planets have been discovered. Even today, by analysing data from telescopes and satellites that have been used to search for them and are no longer active, we continue to find interesting guests around a variety of stars.

Among the latter

Opening of TOI-2257b

The red dwarfs are particularly interesting objects to search for exoplanet using a transit method. The brightness of the star we have discovered can be reduced by passing an exoplanet in front of it. The small size of the Mcarlics increases the variation in the light flux of this star, which becomes easily observed by our telescopes.

NASA ' s TESS satellite observed the star TOI-2257 for four months in four different sectors of the sky. After reworking the data, researchers discovered two signals called glitter curves caused by an object passing in front of a dwarf. These curves reflect a decrease in the brightness of the star. The time distance between these two signals is 176 days. Since TESS observations were not continuous, it is possible that some planetal transits were not registered, so the orbital period may be different. Options include time intervals of 35, 44, 56 and 88 days.

Many ground-based telescopes were designed to search for an exoplanet around red dwarfs classified as M-carlicks, one of which is SAINT-EX, an observatory located in Mexico, which observed the planet twice in a row and determined the right orbital period. TOI-2256b takes 35 days to make one turn around its star.

Eccentric inhabited area

Another feature that makes M-carlicks intrigued is the position of the inhabited area, which determines the distance from the star at which liquid water can be measured. The Carlic stars, cold, have an area very close to them. The search for planets near the stars is much easier, though more difficult, than the search for worlds far away from them. For this reason, the observation of red dwarfs is much more likely to identify planets that are potentially fit for life.

Its temperature varies between -80 °C and +100 °C, but there is one feature that shouldn't be underestimated. Its orbit is very eccentric, and although it has a moderate climate, it may not be suitable for the development of life. Thanks to eccentricity equal to 0.4, outwardly small, but far from that, this exoplanet wins the title of the most eccentric dwarf transit planet ever discovered.

The eccentric orbit is very often characterized by the presence of a gigant planet in the system. For this reason, the possible existence of a giant companion has been studied by means of a transit method, but without any evidence; no less effective is the search for other planets in the system, especially if they are massive and remote from the central star, as in this case, the radiance method; this analysis shows a shift in the spectrum of the star as it moves around the baricent of the planetary system.

This technique can measure the mass of the planets and identify the associates orbiting the same star. In addition to this further analysis, which is needed to clearly determine the density of the planet, which requires both the mass and the radius to be known, the TOI-2257b will also be monitored by the atmosphere. This is one of the few planets that are candidates for observation by JWST using transmission spectroscopy. This technique allows the upper atmosphere of the planets to be studied by analysing changes in the spectrum of the stars around them.

And while James Webb is moving tirelessly towards its ultimate goal, exoplanet hunters continue to find interesting targets for powerful mirrors of the largest space telescope ever built by man, such as the eccentric subneptun object TOI-2257b.