A new world has just been found orbiting a Sun-like star only 20 light-years away, and it could be one of the most promising places to study Earth-like atmospheres.

Scientists have confirmed the existence of HD 20794 d, a super-Earth that takes 647 days to orbit its star, placing it within the habitable zone — the region where liquid water might exist. This breakthrough, built on more than two decades of observations, opens the door to studying planetary atmospheres with next-generation telescopes.

Discovery of a New Super-Earth

The Instituto de Astrofísica de Canarias (IAC) and the Universidad de La Laguna (ULL) have confirmed the discovery of a super-Earth orbiting in the habitable zone of HD 20794, a nearby Sun-like star. This finding, based on more than 20 years of observations, provides a valuable opportunity to study the atmospheres of Earth-like planets in greater detail.

Searching for planets in the habitable zones of Sun-like stars is key to understanding the potential for life beyond Earth. It also helps scientists explore conditions similar to those that allowed life to develop on our own planet. HD 20794, a star slightly smaller than the Sun and located just 20 light-years away, has long been a subject of scientific interest. This latest discovery marks the third planet identified in its system, following the confirmation of two other super-Earths more than a decade ago.

A Super-Earth in the Habitable Zone

The newly discovered planet, HD 20794 d, is a super-Earth with a mass six times that of Earth. It takes 647 days to complete one orbit around its star — about 40 days less than Mars’ orbit around the Sun. This orbit places it within the star’s habitable zone, meaning it is at a distance where liquid water could potentially exist on its surface, one of the essential ingredients for life as we know it.

It is precisely the combination of the planet’s distance from its star and the proximity of the system that makes it particularly attractive, rendering it a perfect candidate for observations with the ELT, ESO’s 40-meter telescope, or future space missions by ESA and NASA. “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 S.L., a doctoral student at the Universidad de La Laguna and the study’s lead author, published recently in the journal Astronomy & Astrophysics. “In fact, we know of very few similar planets,” notes Alejandro Suárez Mascareño, a researcher at the IAC and co-author of the work. “This will surely be one of the first we can study,” adds.

Two Decades of Cutting-Edge Observations

This discovery was made possible thanks to over 20 years of radial velocity measurements from the ESPRESSO and HARPS spectrographs, both installed at ESO observatories in Chile. These instruments, among the most advanced in the world, can measure the tiny variations in stellar velocity caused by the gravitational pull of planets in a system. “Very few instruments in the world can achieve the level of precision required for a discovery like this,” explains Nicola Nari.

To go even further, the team applied sophisticated processing techniques to the spectra obtained. “We worked on data analysis for years, gradually analyzing and eliminating all possible sources of contamination,” explains Michael Cretignier, a co-author of the study and researcher at the University of Oxford. This meticulous 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 we have a robust detection,” adds Nathan Hara, a researcher at the Marseille Astrophysics Laboratory.

What Does This Mean for Habitability?

Although the planet is located in the system’s habitable zone, it is too early to say whether it could host life. Its high mass and eccentric orbit make it a very different world from ours. Unlike 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 the conditions for habitability vary over time and how these variations may influence the evolution of the planet’s atmosphere,” says Alejandro Suárez Mascareño, researcher at the IAC and co-author of the work.

Explore Further:

Reference: “Revisiting the multi-planetary system of the nearby star HD 20794 – Confirmation of a low-mass planet in the habitable zone of a nearby G-dwarf” by N. Nari, X. Dumusque, N. C. Hara, A. Suárez Mascareño, M. Cretignier, J. I. González Hernández, A. K. Stefanov, V. M. Passegger, R. Rebolo, F. Pepe, N. C. Santos, S. Cristiani, J. P. Faria, P. Figueira, A. Sozzetti, M. R. Zapatero Osorio, V. Adibekyan, Y. Alibert, C. Allende Prieto, F. Bouchy, S. Benatti, A. Castro-González, V. D’Odorico, M. Damasso, J. B. Delisle, P. Di Marcantonio, D. Ehrenreich, R. Génova-Santos, M. J. Hobson, B. Lavie, J. Lillo-Box, G. Lo Curto, C. Lovis, C. J. A. P. Martins, A. Mehner, G. Micela, P. Molaro, C. Mordasini, N. Nunes, E. Palle, S.P. Quanz, D. Ségransan, A. M. Silva, S. G. Sousa, S. Udry, N. Unger and J. Venturini, 28 January 2025, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/202451769

Researchers from the IAC, including Jonay I. González Hernández, Atanas K. Stefanov, Rafael Rebolo, Carlos Allende Prieto, and Enric Pallé, also contributed to this publication.