A team of scientists led by the Instituto de Astrofísica de Canarias (IAC) has validated new planets orbiting red dwarf stars located in a region known as the Neptune Desert, where few Neptune-like planets have been found. This discovery is documented in the journal Astronomy & Astrophysics.
The research, part of a Master’s thesis by Alberto Peláez Torres, was guided by Emma Esparza Borges and Enric Pallé Bagó. It utilized data from the MuSCAT2 instrument at the Carlos Sánchez Telescope in Tenerife and the TESS (Transiting Exoplanet Survey Satellite) mission to confirm as many exoplanet candidates as possible.
The study aimed to clarify the planetary nature of thirteen TESS Objects of Interest (TOIs), which could either be planets or other celestial bodies such as brown dwarfs or binary star systems. The host star plays a crucial role in determining the nature of these unclassified planetary objects.
Researcher Alberto Peláez noted that M-type stars are particularly suitable for detecting small planets due to their low temperature and size, which reduces the contrast between the star and the planet's radius.
Emma Esparza emphasized that this work validates multicolor transit photometry as an effective technique for confirming or ruling out the planetary nature of TESS candidates.
The innovative methodology involved observing a star's brightness through different color filters, utilizing ground-based instruments alongside high-resolution observations and TESS light curves. The team successfully validated five TESS exoplanet candidates: TOI-1883b, TOI-2274b, TOI-2768b, TOI-4438b, and TOI-5319b.
Notably, several validated planets, particularly TOI-2768b, are located in the Neptune Desert, characterized by the scarcity of Neptune-sized planets. This region, defined by a lack of planets with sizes four times that of Earth, raises questions about physical phenomena that may deplete such planets, including atmospheric mass loss from high-energy stellar irradiation.
Peláez highlighted the importance of discovering planets in the Neptune Desert for advancing exoplanet studies, as investigating their atmospheres could provide insights into the phenomena affecting these planets.
The MuSCAT2 team, comprising international researchers from Spain and Japan, continues daily monitoring of stars that may host planets, aiming to discover and validate new celestial bodies. This ongoing effort will complement the findings of the TESS mission.
Over the years, planetary discoveries have shown that the Neptune Desert, a concept introduced in 2016, does not align with the current distribution of exoplanets, which typically have orbital periods of one to four days and sizes between two to six times that of Earth.