Instrument breaks record and detects exoplanet with only 40% of Earth's mass

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.

Comparison between the equilibrium temperature, in Kelvin, from Mercury, Venus and Earth and that of the planets of the L system 59-45. The fourth planet, d, is dotted because the diameter is unknown, and the fifth is yet to be confirmed. (Credit: ESO)

Planets b, c and d have very short periods, completing a circle around their star every 2.2, 3.7 and 7,35 Earth days, respectively. This close, they are certainly uninhabitable, even taking into account the fact that L 98-45 a red star an, smaller and cooler than the Sun. Still, they arouse interest. And the combination of mass and diameter data makes it possible to estimate its density and, therefore, project the possible composition. dry. The third of them, d, seems to be a planet that has 30% of its mass in water, what would make it an ocean world. Despite this, the temperature probably makes it uninhabitable.

In addition, the radial velocity data indicated the presence of a fourth planet, which had not been identified by Tess, with a mass of at least three times larger than Earth’s and a period of 08, 8 days. There are also signs of a fifth planet, this one has not yet been confirmed, with a period of 30 days. If it exists, it must be right in the middle of the system’s so-called habitable zone, where the distance to the star would allow for the presence of liquid water in a stable manner on the surface.

In addition to breaking sensitivity records in the detection of planets by radial velocity, the important finding for the future of research on these objects. The L system 59-59 is near the enough to allow the James Webb Space Telescope, to be launched later this year, to attempt to probe the atmospheric composition of its planets.

ThisColumn published on Mondays, in Folha Corrida.

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