Astronomers are captivated by the L 98-59 system, just 35 light-years from Earth. It hosts one of the smallest rocky exoplanets known, a water-dominated world, and possibly an Earth-like planet in the habitable zone.
Central to this fascinating system is the red dwarf star L 98-59 (also known as TOI-175). Two years ago, NASA's TESS mission detected three Earth-sized planets orbiting it using the transit method, which measures dips in starlight as planets pass in front.
While transits reveal planetary radii, determining mass is crucial for calculating density and inferring composition. A recent study addressed this using radial velocity measurements.
Radial velocity detects a star's subtle wobble due to orbiting planets' gravitational pull around the system's center of mass. By analyzing shifts in the star's light spectrum, scientists isolate these effects to compute planetary masses.
Published in Astronomy & Astrophysics, the study leveraged the European Southern Observatory's Very Large Telescope (VLT) in Chile. It confirmed the three planets and provided detailed insights: L 98-59b is among the smallest rocky exoplanets discovered, with roughly half Venus's mass.
Analyses suggest L 98-59b and its neighbor have small iron cores with traces of water in their atmospheres. The third planet shares a similar core but holds far more water—up to a third of its total mass.
The observations also indicate a fourth rocky planet and evidence for a potential fifth in the habitable zone, receiving Earth-like stellar flux.
Further data is needed to confirm the fifth planet, but if verified, it could become a prime target for the James Webb Space Telescope. Once fully operational, JWST will probe its atmosphere for potential biosignatures.
