Researchers confirm existence of habitable zone exoplanet

Researchers confirm existence of habitable zone exoplanet
by Sophie Jenkins
London, UK (SPX) Feb 18, 2025

An international team of astronomers has validated the discovery of a super-Earth positioned within the habitable zone of a nearby Sun-like star. Initially detected two years ago by Oxford University scientist Dr. Michael Cretignier, the planet's existence has now been confirmed following an extensive analysis of observational data spanning more than 20 years. The findings, which offer new opportunities to explore potentially life-supporting exoplanets, have been published in Astronomy and Astrophysics.

Named HD 20794 d, the planet possesses a mass six times that of Earth and orbits a star located just 20 light-years away. The planet's orbit places it within the habitable zone, meaning it occupies a region where liquid water could potentially exist on its surface, an essential criterion for life as we understand it.

Dr. Cretignier initially identified the candidate exoplanet in 2022 while analyzing archived data collected by the HARPS (High Accuracy Radial Velocity Planet Searcher) spectrograph at Chile's La Silla Observatory. His findings were based on periodic variations in the spectrum of light emitted by the star, which suggested the gravitational influence of an orbiting planet. However, given the signal's subtle nature, its origin remained uncertain-it could have been the result of stellar activity, instrumental noise, or an actual planetary presence.

To confirm the planet's existence, a global collaboration of scientists examined precise measurements taken over two decades by HARPS and its successor, ESPRESSO, also based in Chile. These instruments rank among the most advanced globally for detecting minuscule shifts in light spectra.

"We spent years refining our data analysis, meticulously ruling out all potential sources of interference," explained Dr. Cretignier. The team employed sophisticated analytical techniques to differentiate the planetary signal from background noise and instrument-related fluctuations. By integrating data from both instruments, they achieved a definitive confirmation of HD 20794 d's presence.

"It was an incredible moment when we could finally confirm the planet's existence," Dr. Cretignier shared. "Given that the initial detection was near the spectrograph's sensitivity threshold, there was always some uncertainty. Its relative proximity-just 20 light-years away-raises the exciting possibility of future space missions capturing direct images of it."

While HD 20794 d resides within its system's habitable zone, its suitability for life remains uncertain. Unlike most planets, its orbit is elliptical rather than circular, meaning it traverses the habitable zone's outer and inner edges throughout its orbit. This fluctuation in distance from its star introduces temperature variations that could impact its potential for hosting life.

Despite these uncertainties, HD 20794 d serves as an invaluable target for next-generation space telescopes aimed at identifying life beyond our solar system. Observatories such as the Extremely Large Telescope, the Habitable Worlds Observatory, and the Large Interferometer For Exoplanets (LIFE) are designed to analyze the atmospheres of nearby exoplanets, searching for chemical signatures that may indicate biological activity.

Reflecting on the discovery, Dr. Cretignier remarked, "My primary focus is on finding these hidden worlds, but I am eager to see what other researchers will uncover about this planet. Given its proximity and unusual orbit, HD 20794 d represents one of the most intriguing Earth-like exoplanets we have encountered."

Research Report:Revisiting the multi-planetary system of the nearby star HD 20794