Three decades after the first exoplanet was discovered, astronomers have identified over 7,000 exoplanets in our galaxy. Yet, countless more await discovery. Researchers are now delving into the characteristics of these planets to uncover the possibility of extraterrestrial life. This pursuit has led to the discovery of super-Earth HD 20794 d, thanks to a collaboration involving the University o by Robert Schreiber
Berlin, Germany (SPX) Jan 29, 2025
Three decades after the first exoplanet was discovered, astronomers have identified over 7,000 exoplanets in our galaxy. Yet, countless more await discovery. Researchers are now delving into the characteristics of these planets to uncover the possibility of extraterrestrial life. This pursuit has led to the discovery of super-Earth HD 20794 d, thanks to a collaboration involving the University of Geneva (UNIGE) and the NCCR PlanetS. Situated in an eccentric orbit that transitions in and out of its star's habitable zone, this discovery is based on two decades of meticulous observations using the world's leading telescopes. The findings are detailed in the journal Astronomy and Astrophysics.
"Are we alone in the Universe?" This ancient question, once rooted in philosophy, has gained traction in modern science with growing evidence and hypotheses. Astronomical discoveries, such as the identification of the first exoplanet orbiting a star other than the Sun in 1995, have significantly advanced this quest. This groundbreaking discovery earned Michel Mayor and Didier Queloz of UNIGE the Nobel Prize in Physics in 2019.
Since then, astronomers have uncovered thousands of exoplanets, with consensus pointing to the likelihood that nearly every star hosts a planetary system. Research now focuses on identifying planets with distinct characteristics, such as HD 20794 d, which is of particular interest due to its location in the habitable zone.
A promising target in the habitable zone
HD 20794 d is classified as a super-Earth, a rocky planet larger than Earth. It is part of a planetary system containing two other planets and orbits a G-type star - similar to the Sun - located just 19.7 light-years away. This proximity makes it easier to study due to stronger and more visible light signals. "HD 20794, the star around which HD 20794 d orbits, is not an ordinary star," explained Xavier Dumusque, Senior Lecturer and researcher at UNIGE. "Its brightness and closeness make it an ideal target for upcoming telescopes designed to observe exoplanetary atmospheres."The key interest in HD 20794 d lies in its position within the star's habitable zone, where conditions may allow liquid water to exist - a vital prerequisite for life as we know it. For G-type stars like HD 20794, this zone typically spans 0.7 to 1.5 astronomical units (AU). HD 20794 d's orbital period of 647 days places it at varying distances, oscillating between the inner and outer edges of this zone. This eccentric orbit enables scientists to refine theoretical models and test hypotheses about planetary habitability. If water exists on HD 20794 d, it may transition between ice and liquid states during its orbital path, potentially creating favorable conditions for life.
Two decades of research and innovation
Detecting HD 20794 d required years of iterative analysis. Researchers studied over 20 years of data collected by cutting-edge instruments such as ESPRESSO and HARPS. The team also utilized YARARA, an advanced data reduction algorithm developed at UNIGE, to filter out noise that previously obscured planetary signals. "We analyzed the data for years, carefully eliminating sources of contamination," noted Michael Cretignier, a postdoctoral researcher at Oxford University and developer of YARARA during his PhD at UNIGE.HD 20794 d offers a valuable opportunity for modeling and testing new ideas in the search for extraterrestrial life. Its proximity and the brightness of its host star make it an excellent candidate for next-generation instruments, such as the ANDES spectrograph for ESO's Extremely Large Telescope (ELT). Determining whether this planet harbors life will require significant scientific advancements and interdisciplinary efforts. Research into the conditions for its habitability is already underway at UNIGE's Centre for Life in the Universe (CVU).
Research Report: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
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