The question “Are we alone in the Universe?” has been a philosophical topic for thousands of years. Only recently has modern science started to provide solid hypotheses and evidence to address it. Astronomers are making slow progress, and each discovery, whether theoretical or observational, helps expand our understanding.
Thirty years after discovering the first exoplanet, we’ve identified over 7,000 in our galaxy. However, billions more remain to be discovered. Exoplanetologists are now focusing on their characteristics to find potential signs of life elsewhere in the Universe.
An international team, including the UNIGE and the NCCR PlanetS, has discovered a super-Earth HD 20794 d. It is larger than the Earth and part of a planetary system containing two other planets.
The new planet lies in an eccentric orbit, moving in and out of its star’s habitable zone. It orbits a G-type star—HD 20794—similar to the Sun, located only 19.7 light-years away. On the scale of the Universe, this is in the very close neighborhood of the Earth. This proximity makes studying easier, as its light signals are more visible and stronger.
Xavier Dumusque, Senior Lecturer and researcher in the Department of Astronomy at the UNIGE and co-author of the study, said, “HD 20794, around which HD 20794 d orbits, is not an ordinary star. Its luminosity and proximity make it an ideal candidate for future telescopes whose mission will be to observe the atmospheres of exoplanets directly.”
Planet HD 20794 d is fascinating because it’s located in its star’s habitable zone, where liquid water could exist—an essential condition for life. This zone varies based on stellar properties and, for stars like the Sun or HD 20794, spans from 0.7 to 1.5 astronomical units (AU).
HD 20794 d takes 647 days to orbit its star, similar to Mars, but its orbit is elliptical, causing it to move in and out of the habitable zone. This makes it an exciting study subject for astronomers. If water exists on this planet, it could change from ice to liquid during its orbit, creating conditions favorable for life.
Detecting the super-Earth HD 20794 d was challenging, requiring over twenty years of data analysis using advanced instruments like ESPRESSO and HARPS. Scientists used a data reduction algorithm called YARARA to filter out noise and identify planetary signals.
The discovery of HD 20794 d provides a valuable opportunity for scientists to model and test new hypotheses in the search for extraterrestrial life. Its proximity to a bright star makes it an ideal target for future instruments like the ANDES spectrograph for ESO’s Extremely Large Telescope (ELT).
Determining if this planet can support life will need multiple scientific advancements and a multidisciplinary approach. The new Centre for Life in the Universe (CVU) at UNIGE’s Faculty of Science is already studying its habitability conditions.
Journal Reference:
- 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. 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. Astronomy & Astrophysics (A&A). DOI: 10.1051/0004-6361/202451769
Source: Tech Explorist
