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The Neptunian desert is a statistical anomaly of ice giants in close orbits around their host stars.
Illustration of a Hot Neptune exoplanet. (Image Credit: News9).
New Delhi: Scientists from the Physical Research Laboratory have discovered a sub-Saturn exoplanet designated as TOI-6651 b, in a close orbit around the host star. Scientists know of over 5,500 exoplanets, or worlds in orbits around stars other than the Sun, but only 74 of these are in the mass gap between Neptune and Saturn, known as sub-Saturns. Only 41 of these have orbital periods less than 10 days, and are hot sub-Saturns, that are in what is known as the hot Neptune desert, which is a glaring and mysterious lack of gas giants smaller than Jupiter in close orbits around their host stars.
The exoplanet discovered by the researchers is a hot and dense sub-Saturn, that moves across or transits the host star, which is similar to the Sun. The findings are based on data from NASA’s TESS (Transiting Exoplanet Survey Satellite) and the PARAS Advanced Radial velocity Abu Sky Search-2 (PARAS-2) instrument operated by the Physical Research Laboratory. Apart from determining the characteristics of the newly discovered exoplanet, the researchers from PRL have also improved the scientific understanding of the star itself. The researchers have also determined the mechanism by which the hot Neptune was formed.
How TOI-6651 b was formed
Hot Neptunes are rare planets that are assembled in hostile conditions. TOI-6651b is not a failed gas giant, in that it is not one of those Neptune-sized worlds that could not accrete enough material. Instead, the exoplanet has lost gas from its outer atmosphere, or has been stripped away. This gas has not escaped because of photoevaporation, or because of the energetic outpourings from the host star. The researchers believe that the exoplanet had an eccentric or elliptical orbit, that resulted in tidal heating, that provided the necessary energy for the gas to escape. A paper describing the findings has been published in Astronomy and Astrophysics.
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