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Astronomers using NASA's Transiting Exoplanet Survey Satellite (TESS) have discovered two exoplanets orbiting the star TOI-6054, located about 259 light-years from Earth. Both worlds are sub-Neptunian and have densities that suggest they may have a gaseous envelope.
The Transiting Exoplanet Survey Satellite (TESS) is a space telescope that allows scientists to observe transits of the brightest stars in our galaxy – regular dips in brightness when a planet passes in front of a star. Since its launch in April 2018, the astronomical instrument has helped find more than 7300 exoplanet candidates (so-called TOIs), of which 595 have been confirmed by other observations.
Now, TESS-recorded changes in the brightness of the star TOI-6054, which has begun to transition to the subgiant stage (i.e., the hydrogen needed for nuclear fusion is running out), made it a suitable target for additional spectroscopic research, implemented within the framework of the OrCAS program. The 6 billion-year-old star was confirmed using the NEID spectrograph installed on the three and a half meter WIYN telescope in Arizona (USA).
In a paper published on the Cornell University preprint server, an international research team led by Maxwell A. Kroft of the University of Wisconsin-Madison reported that both planets are sub-Neptune worlds, with the size of Earth and Neptune. (TOI-6054b) completes a full orbit around its star in 7,5 days, while the other (TOI-6054c) takes 12,56 days.
As TOI-6054 expands and becomes brighter over several hundred million years, both sub-Neptunes receive 300-600 times more radiation from the star than Earth does from the Sun. Moreover, their orbital periods around their parent star are synchronized by gravitational interactions.
Calculations also showed that due to intense heating, the sub-Neptune TOI-6054b is likely losing its atmosphere. This process can be verified by observing the spectral line of helium (occurs when electrons in helium atoms transition from one energy level to another) and the Lyman-alpha line (the resonance line of hydrogen) - with intense atmospheric blowing, traces of these lines will be clearly visible in the spectrum.
Astronomers noted that the star TOI-6054 is quite bright, observations using the James Webb Space Telescope and other astronomical instruments can help to analyze in detail the chemical composition of the atmospheres of both planets. Further studies can shed light on the formation of sub-nephews and check how exactly stellar evolution affects the properties of planets. In particular, analysis of the gas composition of TOI-6054b and TOI-6054c will allow to clarify the "universality" of the mechanism of formation of such worlds and the role of planetary migration in the early stages of the evolution of planetary systems.
