This artist’s impression shows L 98-59b, one of the planets in the L 98-59 system 35 light-years away.

(ESO/M. Kornmesser)

The planets that are beyond the bounds of our solar system are known as exoplanets. The universe is vast, and so far, experts have found thousands of them out there in the cosmic world. Therefore, the possibilities of having a world similar to ours where the conditions might be just right for life as we know it remains very high, and astronomers are in a relentless pursuit to find clues of such worlds outside our solar system.

Towards this, astronomers recently discovered a new star system that hosts at least five unique worlds, with some showing similarities to the planets in our solar system. This newly found planetary star system is L 98-59, and is located about 35 light-years away from Earth.

“We have hints of the presence of a terrestrial planet in the habitable zone of this system,” explains Olivier Demangeon, a researcher at the University of Porto in Portugal and lead author of the new study.

Discovery of the star system

In 2019, NASA’s Transiting Exoplanet Survey Satellite (TESS) spotted planets orbiting the star. Since then, astronomers have been studying this system as these discovered planets are close to the host star. This proximity bestows them with the ideal amounts of warmth similar to the terrestrial planets of our solar system, such as the Earth or Venus.

At first, scientists found three planets that fascinated them with distinct features. These exoplanets exhibited evidence of the presence of some percentage of water. The researchers also highlight that two planets—likely to be dry and rocky worlds—might contain a tiny amount of water because of their proximity to the star. Meanwhile, the mass of the third planet is likely to be made of 30% water, indicating that it might be an ocean world.

‘Hidden’ world in the habitable zone

Surprisingly, the team discovered clues of ‘hidden’ worlds in this star system during their observations using the European Southern Observatory’s Very Large Telescope in Chile. The telescope observations helped them unravel several details about the other exoplanets of this alien star system while indicating the presence of two more planets that no one had spotted before.

After discovering the fourth ‘hidden’ planet in the system, scientists now suspect the presence of one more world. Among all, this potential fifth planet could be a lucky draw! The planet is theorised to be orbiting just at the right position in the star system, i.e., the habitable zone.

“The planet in the habitable zone may have an atmosphere that could protect and support life,” says María Rosa Zapatero Osorio, an astronomer at the Centre for Astrobiology in Madrid, Spain, and one of the authors of the study.

Technical breakthrough

Moreover, another significant breakthrough of this study has been estimating the mass of the lightest exoplanet measured to date using the radial velocity technique. This technique takes into account the wobble of the star from some gravitational tug of its orbiting planets. The team found the innermost planet of the new star system to be the lightest among all the known exoplanets of this system—equivalent to half the mass of Venus.

The researchers used the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) instrument on ESO’s VLT to study L 98-59. “Without the precision and stability provided by ESPRESSO this measurement would have not been possible,” says Zapatero Osorio. “This is a step forward in our ability to measure the masses of the smallest planets beyond the Solar System.”

This study could prove to be another important milestone in the hunt for life beyond our home planet. The results of this study have been published in the journal Astronomy & Astrophysics and can be accessed here.

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