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Even barely half the mass of Venus is reached by a dwarf exoplanet orbiting in the habitable zone at a distance of 35 light-years

In Chile, the European Southern Observatory’s Very Large Telescopes (ESO VLT) were used by a group of astronomers to gather new information about planets similar to the inner planets of the Solar System orbiting the nearby star L 98-59. One is only half the mass of Venus – making it the smallest exoplanet observed by the radial velocity method – and probably orbits in the habitable zone of its star, its surface covered in water.

“A planet orbiting in a residential area could also have an atmosphere that could protect and sustain life on it.” Started by Maria Rosa Zapatero Osorio, an astronomer at the Astrobiology Center in Madrid (Madrid, Spain), and co-author of a study published in the Journal of Astronomy and Astrophysics.

The result is an important step in finding traces of life on exoplanets, similar in size to Earth. In an exoplanet, the so-called detectability of biomarkers depends largely on our ability to study the atmosphere, but our current telescopes are not large enough to achieve the required resolution of small rocky planets. The planetary system now studied, marked L 98-59 after its star, would be an attractive target for future projects to observe the atmosphere outside the solar system. It’s only 35 light-years away, and the new results show that rocky planets like Earth and the orbit of Venus are close enough to their stars to be high enough in temperature.

Based on ESO VLT measurements, the group concluded that as many as three of the planets may contain water within or in their atmosphere. It is possible that the two planets closest to the star in the L 98-59 system are dry, although the presence of small amounts of water cannot be excluded, but up to 30% of the mass of the third planet may be water, that is, it may be. ocean planet.

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The group also found a planet “hiding” so far in the system that had not been pointed out by previous observations. So a fourth planet was discovered, but it is believed that there can be five in the system, that is, in the same region where water in its liquid state can exist on its surface. “We’ve discovered evidence that a planet similar to Earth might be orbiting in the system’s habitable zone.” – explains Olivier Demangon (Instituto de Astrofísica e Ciências do Espaço, University of Porto, Portugal), lead author of the new study.

The imaginary graphic shows one of the planets of the L 98-59 system with a duration of 35 light years, L 98-59b. Four rocky planets have been proven in the system, but there may be a fifth, but its existence has not yet been confirmed (ESO / M. Kornmesser)

The result is also a technical breakthrough: astronomers were able to use the radial velocity method to measure that the mass of the planet closest to the star in the system is only half the mass of Venus. Thus, it is the smallest exoplanet whose coefficient is determined in this way, that is, by measuring the oscillation of the star planet due to the gravitational “pull”.

The research team used the ESPRESSO VLT (Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) to study L 98-59. “Without the accuracy and stability of ESPRESSO, this measurement would not have been possible” Zapatero Osorio says: “We have taken another step towards being able to determine the mass of even the smallest exoplanets.”

Diagrams compare the outer planet system L 98-59 (above) to the inner part of the Solar System (Mercury, Venus, and Earth), highlighting the similarities between the two. In the graphs, the distances of the planets from a star to each other are not realistic. The diagram has been modified to correspond to the habitable zones of the Solar System and L 98-59. As can be seen from the graphs, which also show the temperature scale given in Kelvin (K), planet Earth and V, which has not yet been confirmed from L 98-59, receive approximately the same amount of radiation from their stars. Assuming that the atmospheres of two planets are similar, the average surface temperature of the fifth planet may be similar to the surface temperature of the Earth, which is favorable for the presence of water in the liquid state (ESO / L. Calçada / M. Kornmesser) Acknowledgments: O. Demangeon ))

Astronomers first discovered the three planets L 98-59 in 2019, based on measurements from NASA’s TESS Space Telescope (Transiting Exoplanet Survey Satellite). This space telescope uses the transit method – a slight decrease in the brightness of stars due to a planet passing in front of its star in its orbit – to detect planets and determine their size. However, Demangeon and his team were unable to detect the presence of two additional planets and determine the size of the first three based on radial velocity measurements using ESPRESSO and its predecessor, HARPS (High Resolution Radial Velocity Researcher) on ESO’s 3.6-meter telescope. “If we want to know what a planet is made of, we need to know at least its mass and radius.” Demangeon explains.

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The group is confident that the research will be able to continue at NASA/ESA/CSA JWST (James Webb Space Telescope) ESO’s extraordinary binoculars are currently under construction in the Atacama Desert in Chile and are scheduled to be commissioned in 2027 (ELT) would also be an ideal tool for studying these planets. “The accuracy of the ELT HIRES instrument may be sufficient to study the atmospheres of planets orbiting the L 98-59 system, thus supplementing JWST observations with terrestrial observations.” – Zapatero Osorio’s odds flashes.

This system is indicative. Dimangon concludes. “Humanity has actually been searching for Earth-like planets since the birth of astronomy, and today we are finally getting closer and closer to discovering a terrestrial planet orbiting in the habitable zone of its star and studying its atmosphere.”

The following video – Uncovering the Secrets of a Nearby Planetary System (ESOcast Light 242) – summarizes new knowledge about the L 98-59 planetary system.

Source: eso2112en – Scientific Publications