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This tiny exoplanet 35 light-years away is half the mass of Venus

The L 98-59b planet.
This artist’s impression shows L 98-59b, one of the planets in the L 98-59 system that’s 35 light-years away. The system contains four confirmed rocky planets with a potential fifth, the farthest from the star, unconfirmed. ESO/M. Kornmesser

Of the roughly 4,200 planets outside our solar system discovered thus far, most are larger than Earth for the simple reason that it’s easier to spot a larger planet as it has a more noticeable impact on the environment around it. That’s why it’s notable when smaller exoplanets are discovered, like the recently identified planet L 98-59b, which is just half the mass of Venus.

The planet, orbiting the star L 98-59, which is just 35 light-years away, is part of a system of four or possibly five planets that are comparable to the rocky planets in the inner part of our solar system. The diminutive planet is the closest of the system to its star and is the smallest ever discovered using a method called radial velocity. This works by detecting a tiny wobble in the host star, which is caused by the gravity of the planet as it orbits, and this detection was made using the European Southern Observatory’s Very Large Telescope (VLT), which is located in the Atacama desert in Chile.

The other planets in this system are intriguing as well. One of them may even be habitable, as it is in the habitable zone (the distance from a star at which liquid water could exist on a planet’s surface), and it is a rocky planet like Earth or Venus.

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

This makes the system a great target for further investigations with new and upcoming tools, like the James Webb Space Telescope, which will be able to detect whether exoplanets have atmospheres.

“This system announces what is to come,” said lead author Olivier Demangeon of the University of Porto. “We, as a society, have been chasing terrestrial planets since the birth of astronomy, and now we are finally getting closer and closer to the detection of a terrestrial planet in the habitable zone of its star, of which we could study the atmosphere.”

The findings are published in the journal Astronomy & Astrophysics.

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