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Astronomers have discovered two exoplanets near the star TOI-6054, located about 259 light-years away. The discovery was made using NASA's TESS space telescope. Both new worlds belong to the sub-Neptune class - their density indicates the possible presence of a significant gas envelope.
The TESS space telescope observes millions of stars, recording regular “dips” in brightness when a planet passes in front of its parent star. Since its launch in April 2018, TESS has discovered more than 7300 possible exoplanets (TOIs), of which 595 have already been confirmed by further studies.
The star TOI-6054, which is entering a subgiant phase (the reserves of hydrogen for nuclear reactions are exhausted), turned out to be an interesting target for additional spectroscopic analysis within the framework of the OrCAS program. Observations were made using the NEID spectrograph on the WIYN telescope (3,5 meters in diameter) in Arizona. As a result, astronomers confirmed the existence of two exoplanets in this star, which formed about six billion years ago.
According to a publication on the Cornell University preprint server, the first of these planets (TOI-6054b) orbits its star in 7,5 days, and the second (TOI-6054c) in 12,56 days. Their radii are approximately 2,6–2,8 times that of Earth, and their masses are 9–12 times those of Earth. These characteristics suggest that each of the planets has a gaseous envelope.
As TOI-6054 expands and brightens over several hundred million years, both sub-Neptunes are exposed to intense radiation, 300–600 times stronger than Earth receives from the Sun. Moreover, their orbital periods are aligned with each other through gravitational interaction.
Calculations suggest that TOI-6054b's hot atmosphere may be actively evaporating. This process can be confirmed by observing the spectral lines of helium and the Lyman-alpha line (hydrogen), which are clearly visible in the case of intense "blowing" of the gas envelope.
Scientists believe that TOI-6054 is a bright enough star to study its planets in detail using the James Webb Telescope and other similar instruments. Further observations will allow us to better understand the chemical composition of the atmospheres of both worlds, analyze the role of stellar evolution in the formation of sub-Neptunians, and assess the impact of possible planetary migration in the early periods of the system's existence.
