Photo credit: science.nasa.gov
The Discovery
A newly identified “super-Earth” is orbiting a Sun-like star at a proximity of around 20 light-years from Earth, presenting the potential to be a habitable planet. However, its extreme temperature fluctuations—ranging from intense heat to severe cold—make its habitability challenging.
Key Facts
This planet, which is the farthest of three confirmed to be orbiting the star HD 20794, has an orbital period of 647 days, similar to Mars. Its orbit is notably eccentric, which results in an elongated path. This unique trajectory allows the planet to swing exceptionally close to the star, where it faces intense heating during part of its year, and then retreat to a distance where it could freeze any water present. These dramatic temperature changes have likely occurred for billions of years, with the planet alternating between these extremes approximately every 300 days.
Details
The exploration of star HD 20794 and its associated planets has been comprehensive, with confirmation of the outer planet being achieved by an international team led by Nicola Nari from Light Bridges S.L. and the Instituto de Astrofisica de Canarias. This research involved meticulous analysis of more than two decades of observational data to clarify the orbits and estimated sizes of all three planets.
Utilizing two precision instruments located at ground-based observatories—HARPS (High Accuracy Radial velocity Planet Searcher) in La Silla, Chile, and ESPRESSO (Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) in Paranal, Chile—the scientists meticulously charted minuscule pulsations in the starlight, indicative of the gravitational effects exerted by orbiting planets.
However, such subtle shifts could also result from phenomena unrelated to orbiting bodies, such as stellar activity or surface spots, which can complicate the interpretation of the data. The researchers dedicated years to closely inspecting these spectral changes, distinguishing genuine planetary signals from background noise or potential instrument errors. They ultimately validated that HD 20794 is a relatively stable star, with minimal disruptive activities that could be mistaken for the presence of planets.
Fun Facts
This unique super-Earth is viewed as an excellent target for forthcoming space missions focused on finding habitable environments and potential signs of extraterrestrial life. Chief among these initiatives is NASA’s Habitable Worlds Observatory, which aims to analyze the atmospheres of Earth-like planets orbiting stars similar to our Sun. Once operational in the coming decades, this observatory will dissect light from these distant worlds to identify the gases present, including those that could indicate biological activity. Given its proximity of only 20 light-years, along with its brightness and relative calm, HD 20974, especially with its extreme temperature variations, stands out as a prime subject for upcoming research by the observatory.
The Discoverers
The international team responsible for confirming the existence of the eccentric super-Earth was spearheaded by Nicola Nari from Light Bridges S.L. and the Instituto de Astrofisica de Canarias. Among them was Dr. Michael Cretignier of the University of Oxford, who first detected hints of the planet back in 2022. Their findings were detailed in a paper titled “Revisiting the multi-planet system of the nearby star HD 20794,” published in the journal Astronomy and Astrophysics in January 2025.
Source
science.nasa.gov