Le disque jeune autour de WRAY 15-1880 peut contenir un système planétaire primitif

Italian astronomers using the European Southern Observatory’s Very Large Telescope (VLT) have identified a potential planetary system forming around the young star WRAY 15-1880, located approximately 492 light-years from Earth. The findings, published on the arXiv preprint server on June 10, suggest that the star’s circumstellar disk, already known to contain a gap, may be in the early stages of planet formation. If confirmed, this would make WRAY 15-1880 one of the few known stars with both a protoplanetary disk and a visible planet detected directly. WRAY 15-1880, also referred to as RX J1842.9-3532, is a classical T Tauri star, a class of young, low-mass stars still in the process of contracting and forming. It resides in the CrA-North subregion of the Corona Australis molecular cloud complex, a well-known stellar nursery. With a mass of roughly 1.24 times that of the Sun and an estimated age of 2.8 million years, the star is relatively close to Earth and thus an ideal target for detailed study of early planetary system dynamics. The star’s circumstellar disk was previously observed to extend up to 87 astronomical units (AU), roughly the distance from the Sun to Neptune, and contains a noticeable gap, suggesting possible clearing by forming planets. The disk itself holds an estimated mass equivalent to 0.01 solar masses, indicating ample material available for planet formation. To investigate further, a team led by Elisabetta Rigliaco of the Astronomical Observatory of Padua in Italy used the VLT’s Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. This advanced tool allows for high-resolution imaging and polarimetric analysis, crucial for detecting faint objects near bright stars. In addition to SPHERE data, the researchers incorporated archival information from other VLT instruments and the Atacama Large Millimeter/submillimeter Array (ALMA), enhancing the depth of their analysis. The observations revealed a companion object potentially orbiting WRAY 15-1880. Based on its spectral characteristics, the object appears to resemble a gas giant akin to Jupiter, with a mass ranging between 1.7 and 7.6 times that of Jupiter. Its surface temperature is estimated at around 1,200 Kelvin, consistent with a T3 spectral type, which typically corresponds to brown dwarfs or low-mass planets. Despite these promising indicators, the research team cautions against definitive conclusions. They acknowledge that the observed signal could arise from multiple factors, including the interplay of starlight with dust in the disk or structural anomalies within the disk itself. These possibilities complicate the interpretation of whether the object is indeed a planet or merely an optical illusion caused by the surrounding environment. According to the study, if the companion is confirmed as a planet, it would orbit WRAY 15-1880 at a distance of about 25.7 AU, placing it in a wide, nearly circular orbit. Such an orbit would take approximately 127 years to complete, far beyond the typical distances of planets in our solar system. This placement suggests that the planet, if it exists, is in a region where gravitational interactions with the central star are minimal, allowing it to maintain a stable trajectory. The implications of such a discovery would be profound. WRAY 15-1880 would join a rare group of stars where both a protoplanetary disk and a planet have been directly imaged. This would provide astronomers with a unique opportunity to observe the earliest phases of planetary formation, offering insights into how planets emerge from the chaotic environments of young stellar systems. Further observations will be necessary to confirm the nature of the companion object. Future studies using more sensitive instruments or longer observational campaigns may help distinguish between a true planet and alternative explanations. Until then, the existence of a nascent planetary system around WRAY 15-1880 remains a tantalizing hypothesis supported by current evidence.