New exoplanet detected with the ESPRESSO spectrograph

Using the Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO), Swiss and Austrian astronomers have discovered a new extraterrestrial world. The new exoplanet orbits a nearby M dwarf star and is at least four times more massive than Earth. The discovery is reported in an article published October 23 on arXiv.org.

ESPRESSO is the state-of-the-art ultra-stable high-resolution spectrograph installed at the Very Large Telescope (VLT) in Chile, covering the spectral range from approximately 380 nm to 788 nm. The instrument is capable of reaching a precision allowing it to detect Earth-like planets around Sun-like stars.

A team of astronomers led by Lia F. Sartori of the Swiss Federal Institute of Technology in Zurich, Switzerland, is conducting a blind ESPRESSO radial velocity search for planets around nearby stars. One of their targets was L 363-38, an M dwarf about 33.3 light-years away. They monitored this star between December 12, 2020 and February 08, 2022, obtaining a total of 31 observations, which resulted in the detection of a new planet.

“In the following, we report the detection and characterization of a planet orbiting the nearby M dwarf star L 363-38. This is one of the few autonomous planet discoveries with ESPRESSO so far. “, wrote the researchers in the article.

The newly detected planet, designated L 363-38 b, has a minimum mass of about 4.67 Earth masses and its radius is estimated to be between 1.55 and 2.75 Earth radii. The exoplanet orbits its host every 8.78 days, at a distance of about 0.048 AU from it, so inside the inner edge of the habitable zone. The equilibrium temperature of L 363-38 b has been calculated at around 330 K.

The parent star L 363-38 (other designations: LHS 1134 and GJ 3049), estimated to be 8 billion years old, has a radius of about 0.274 solar radii and a mass of about 0.21 solar masses. The effective temperature of this star has been measured at 3129 K.

Astronomers speculate that L 363-38 may be orbited by other planets that remain undetected. They explain that based on statistics from NASA’s Kepler and TESS missions, planets around M dwarfs should occur in multiplanetary systems. Therefore, follow-up observations of this planetary system with telescopes such as the James Webb Space Telescope (JWST) are needed in order to discover the presence of other extrasolar worlds around L 363-38.

In their closing remarks, the study authors demonstrate the potential of ESPRESSO in detecting and studying exoplanets around nearby M dwarf stars.

“Indeed, the low luminosity of M stars makes them difficult targets for RV [radial velocity] studies using instruments like HARPS [High Accuracy Radial velocity Planet Searcher] behind a 3.6m telescope, but a spectrograph behind an 8m telescope like ESPRESSO can gather enough light to accurately measure their RV efficiently,” the researchers concluded.

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