News 2024
XMM-Newton's energetic universe joins forces with the Euclid satellite's vision of the sky. A thousand hours of X-ray observations, over a region 40 times the size of the moon, will complement multi-wavelength studies of the cosmic evolution of galaxy clusters. A decisive association to constrain cosmological scenarios and reveal the nature of dark energy.
An international team, including the Astrophysics Department of CEA-Saclay, led by the Instituto de Astrofísica e Ciências do Espaço (IA), utilized one of the world's most advanced spectrographs to detect the smallest "stellar tremors" ever recorded in an orange dwarf star, making it the smallest and coldest star observed to date with confirmed solar oscillations. This study demonstrates that asteroseismology is a powerful technique for studying such stars, opening new perspectives in our understanding of stellar physics and, by extension, exoplanets.
This study is published in the journal Astronomy & Astrophysics Letters: “Expanding the frontiers of cool-dwarf asteroseismology with ESPRESSO: Detection of solar-like oscillations in the K5 dwarf ε Indi”.
The James Webb Space Telescope has produced a new portrait of the atmosphere of exoplanet WASP-39b, a "hot Saturn" some 700 light-years away. After the first near-infrared observations in 2022, which revealed for the first time the presence of sulfur dioxide (SO2) in the atmosphere of an exoplanet, it was observed again in 2023, but this time in the far infrared, using the MIRI spectrometer. This new observation enabled the international research team, including Saclay's Astrophysics Department, to confirm the presence of this molecule in the atmosphere of WASP-39b and to constrain its abundance. This recent study demonstrates that photochemistry shapes the atmosphere of WASP-39b over a wide range of wavelengths.
To unravel this mystery, several teams with diverse skills from the Astrophysics Department had to come together, as the architecture that unites the star to its planet is highly complex. They had to combine a detailed understanding of stellar and planetary physics, exploring their interactions, with a thorough knowledge of the observations made by NASA's Kepler satellite to be able to decipher the data.
The study shows that the observed rarity seems to derive not from observational bias, but rather from physical causes. Tidal effects and magnetism are sufficient to explain qualitatively and quantitatively the migration of nearby planets around fast-rotating stars. Moreover, this migration appears to be dependent on the spectral type (fundamentally linked to mass) of the star. While these results are promising, it is nevertheless necessary to expand the sample size to better constrain scarcity and better understand the mechanisms at play. In particular, this study highlights the importance of considering the spectral type of stars (their masses) if we are to correctly model star-planet interactions.
This work is published in Astronomy & Astrophysics.
