Researchers from the Institute of Astrophysics of the Canary Islands (IAC) and the University of La Laguna (ULL) have confirmed the existence of a super-Earth located in the habitable zone of HD 20794 - a star similar to the Sun but with a lower mass than our Sun, which is located "only" 20 light-years away.
The term "super-Earth" does not say anything about the surface conditions or habitability of the planet. But super-Earths provide important clues about the diversity of planets in our Universe and the possible conditions for life on them.
The newly discovered super-Earth HD 20794 d has six times the mass of Earth and follows an elliptical, rather than circular, orbit. The planet takes 647 days to orbit its sun-like star, which is 40 days less than Mars.
Its orbit provides the right distance from its sun-like star for liquid water to exist on its surface, which is considered a prerequisite for life.
Astronomers as detectives
Astronomy often resembles detective work: in 2022, Dr. Michael Chrétienier of the Institute of Physics at Oxford University discovered an unusual signal while looking through archival data. It may have come from an exoplanet outside our solar system, orbiting a star other than our Sun.
"We worked on the analysis of the data for years, gradually eliminating all possible sources of interference", says Dr Chrétignier, co-author of the study, published in the journal Astronomy & Astrophysics.
Dr Chrétignier used data from ESO's state-of-the-art La Silla Observatory in Chile, which can measure small fluctuations in stellar velocity caused by the gravitational pull of planets in the system, as the basis for his analysis. "Very few instruments in the world can achieve the precision needed for such a discovery", explains Nicolas Nari from the University of La Laguna and lead author of the study.
Now observatories in the Spanish Canary Islands have confirmed Chrétienier's discovery: "For me, of course, it was a great joy to confirm the existence of the planet", says co-author Chrétienier.
Is there life on HD 20794 d?
The planet's interesting distance from its sun-like star and its comparative proximity to Earth make HD 20794 d a promising candidate for future space missions. For now, however, the system will be observed primarily from Earth using high-performance telescopes.
This is because HD 20794 d remains unreachable: with today's technology, traveling to a planet 20 light-years away would take an incredibly long time. Even the longest-traveling probes like "Voyager" would need over 100,000 years to reach a planet that far away.
If there were a space probe moving through space at a speed of 15,000 km/h, it would still need about 16,200 years to travel a distance measured in one light-year. And to cover the 20 light-years in question, which is the distance from Earth to the planet HD 20794 d, the space probe will need a full 324,000 years.
"HD 20794 d is not a second home for humanity, but its location and its peculiar orbit offer us a unique opportunity to study how the conditions for habitability change over time and how these changes can affect the evolution of the planet's atmosphere," says Alejandro Suárez Mascareño from the Canary Islands Institute of Astrophysics and co-author of the study.
Author: Alexander Freund