An international team using the Very Large Telescope, in Chile, managed to accomplish an impressive feat: detecting an exoplanet with about 23% of the Earth’s mass in a star 30 light years away. It was the first time that such a modest-sized world was probed using the radial velocity technique, in which distortions are measured in the star’s light signature as planets revolve around it and make it wobble, due to gravitational interaction.
The feat was only possible thanks to Espresso, a spectrograph installed in 2018 on the VLT which has much higher accuracy than its predecessors . The results of the group led by Olivier Demangeon, from the University of Porto, in Portugal, were accepted for publication in the journal Astronomy & Astrophysics and indicate the presence of at least four planets, possibly five, around the star L 98-59. Three of them were previously known, having been discovered by the satellite Tess in 2019.
NASA’s exoplanet hunting spacecraft detects them by Transit method, measuring the reduction in the star’s brightness as they pass in front of it. This allows you to estimate the diameter of these worlds, but not the mass. The radial velocity technique, in turn, provides the mass but not the diameter. It gives the motivation for the new study.