Science. A rocky exoplanet with a mass of only half of Venus was discovered

Madrid 5 (European Press)

A planet half the mass of Venus – the lightest measured at radial velocity – an ocean world and a possible planet have been discovered in the habitable zone on the nearby star L 98-59.

“Planets in the habitable zone may have an atmosphere that could protect and preserve life,” says Maria Rosa Zapatero Osorio, an astronomer at the Madrid Astronomy Center and one of the authors of the study published in the Journal of Astronomy and Astrophysics.

These findings, together with planets similar to those in the inner solar system, are an important step in the search for life on Earth-sized planets outside the solar system. Detecting biosignatures on an exoplanet depends on the ability to study its atmosphere, but current telescopes are not large enough to achieve the accuracy needed to obtain this information from small, rocky planets.

The recently studied planetary system, named L 98-59 because of its star, is an interesting target for future observations of the atmospheres of exoplanets. Orbiting a star only 35 light-years away, it has been found to host rocky planets, such as Earth or Venus, close enough to the star to be hot.

With the contribution of ESO’s VLT telescope, the team was able to conclude that three of the planets may have water in their interiors or in their atmospheres. Planets in the L 98-59 system are likely to be closer to the star than dry planets, but can contain small amounts of water, while up to 30% of the mass of a third planet can be water, making it an ocean world.

In addition, the team discovered “hidden” exoplanets that had not previously been found in this planetary system. They discovered a fourth planet and suspect a fifth in a region at the correct distance from the star for the presence of liquid water on its surface. “We have indications of a terrestrial planet in the habitable zone of this system,” explains Olivier Demangon, a researcher at the Institute of Astrophysics and Space Sciences at the University of Porto (Portugal) and lead author of the new study.

The study represented a technical advance, as astronomers, using the radial velocity method, were able to determine that the innermost planet in the system has only half the mass of Venus. This makes it the lightest exoplanet measured using this technique, which calculates the star’s wobble caused by the microgravity of the planets orbiting it.

The team used the ESPRESSO instrument (Echelle Spectrograph for Rocky Exoplanets and Stable Spectrographs, Echelle Spectrograph for Stable Spectroscopic Observations and Rocky Exoplanets), installed in ESO’s VLT, to study L 98-59. “Without the accuracy and stability provided by ESPRESSO, this measurement would not have been possible,” says Zapatero Osorio. “This is a step forward in our ability to measure the masses of the smallest exoplanets.”