The Canary Islands Institute of Astrophysics (IAC) and the University of La Laguna have confirmed the discovery of a super-Earth orbiting within the habitable zone of HD 20794, a nearby star similar to the Sun. This international discovery, the result of more than two decades of observations, opens a window for future studies of Earth-like planet atmospheres.
The search for planets in the habitable zone of Sun-like stars is crucial for understanding the possibility of life beyond Earth and for studying conditions similar to those that allowed life to develop on our own planet. In this context, HD 20794, a star with a mass slightly less than the Sun and located only 20 light-years away, has always been the subject of great scientific interest.
The new planet is the third discovered in this system, following the discovery of two super-Earths announced more than a decade ago. Named HD 20794, it is a super-Earth with a mass six times that of Earth and takes 647 days to complete an orbit around its star, 40 days less than Mars. This orbit places it within the system's habitable zone, meaning it is at the right distance from its star to maintain liquid water on its surface, one of the key ingredients for life as we know it.
It is precisely the combination of the distance between the planet and the star, and the proximity of the system, that makes it especially attractive, making it a perfect candidate for observations with the Extremely Large Telescope (ELT), the 40-meter telescope of the European Southern Observatory (ESO), or future space missions from space agencies THAT y POT.
“This is the perfect type of planet for characterizing terrestrial planet atmospheres with next-generation instruments and missions,” explains Nicola Nari, a researcher at Lightbridges SL. and a doctoral student at the University of La Laguna, and lead author of the study, published today in Astronomy & Astrophysics. “In fact, we hardly know of any similar planets,” notes Alejandro Suárez Mascareño, a researcher at the IAC and co-author of the study, who insists that this new planet “will surely be one of the first we can study.”.
This discovery was made possible by studying over 20 years of radial velocity measurements from spectrographs. ESPRESSO y HARPS, both installed in the observatories of THAT, These instruments, among the most advanced in the world, are located in Chile and are supported by the IAC. They are capable of measuring the minute variations in the speed of stars associated with the gravitational pull of the planets in the system. “Very few instruments in the world are capable of providing the level of precision necessary for a discovery like this,” explains Nicola Nari.
With the aim of going even further, the team applied sophisticated processing techniques to the obtained spectra. “We worked on analyzing the data for years, analyzing and gradually eliminating all possible sources of contamination,” explains Michael Cretignier, co-author of the study and researcher at the University of Oxford. This thorough analysis revealed the presence of a candidate signal, identified in 2022. The team immediately launched a new observation campaign to confirm it. “After two years of adding new measurements, we can confirm that we have a robust detection,” adds Nathan Hara, a researcher at the Marseille Astrophysics Laboratory.
Although the planet lies within the habitable zone of the solar system, it is too early to say whether it could support life. Its high mass and eccentric orbit make it a very different world from our own. Unlike the orbits of most planets in the Solar System, HD 20794 d's orbit is not circular but elliptical. Its distance from its star changes significantly, causing the planet to move from the outer edge of the habitable zone to the inner edge throughout its year.
“HD 20794 d is not a second home for humanity, but its position and peculiar orbit give us a unique opportunity to study how habitability conditions vary over time and how these variations can influence the evolution of the planet's atmosphere,” says Alejandro Suárez Mascareño, a researcher at the IAC and co-author of the paper.
Researchers Jonay I. González Hernández, Atanas K. Stefanov, Rafael Rebolo, Carlos Allende Prieto and Enric Pallé from the IAC also collaborated on this publication.
(Text and images provided by the IAC).
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