An international team of astronomers, including researchers from the University of Geneva (UNIGE), has announced the discovery of a super-Earth named HD 20794 d, an exoplanet that may harbor conditions favorable to life. This finding represents another significant step in the search for habitable worlds beyond our solar system.
Since the detection of the first exoplanet, 51 Pegasi b, in 1995, astronomers have cataloged over 7,000 exoplanets in the Milky Way. However, it is estimated that billions more remain to be discovered. In this context, scientists are not only searching for new planets but also investigating their characteristics to assess their potential habitability.
A recent example of this effort is HD 20794 d, an exoplanet orbiting a G-type star, similar to the Sun, located 19.7 light-years from Earth. Its relative proximity makes it a prime target for future observations with next-generation telescopes, capable of analyzing its atmosphere with unprecedented precision.
Classified as a super-Earth, HD 20794 d is a rocky planet with a mass greater than Earth’s and orbits within the habitable zone of its star. This region is crucial as it allows for the existence of liquid water, an essential ingredient for life as we know it.
However, unlike Earth’s nearly circular orbit, HD 20794 d follows an elliptical trajectory, causing it to periodically enter and exit the habitable zone. This peculiarity suggests that, if water is present on the planet, it could alternate between ice and liquid states throughout its orbit, a phenomenon that expands the possibilities for studying habitability under dynamic conditions.
The discovery of HD 20794 d was made possible thanks to two decades of observations using some of the world’s most advanced telescopes, including the ESPRESSO and HARPS spectrographs. A data analysis algorithm developed at UNIGE, called YARARA, played a crucial role in filtering out noise from the observations and confirming the planet’s existence. Its intermittent orbit within the so-called “Goldilocks Zone” makes HD 20794 d an exceptional natural laboratory for investigating planetary habitability.
Astronomers hope that next-generation telescopes, such as the ANDES spectrograph to be installed on the Extremely Large Telescope (ELT) in Chile, will be able to analyze the planet’s atmosphere for biosignatures, such as gases associated with life. The details of the discovery were published in the renowned journal Astronomy & Astrophysics, marking another milestone in the exploration of distant worlds and the search for answers about the existence of life beyond Earth.