New exoplanet HD 20794 d could harbor liquid water
Astronomers have discovered an exoplanet that might have favorable conditions for liquid water. This planet, HD 20794 d, belongs to the group known as super-Earths. It is located in a star system less than 20 light-years away, making it one of the closest candidates for further research.
What distinguishes a super-Earth? As "National Geographic" explains, HD 20794 d is significantly larger than Earth—its mass is more than five times greater, and its radius is twice as much.
It has been classified as a super-Earth, meaning it is a rocky planet with a much greater mass than our planet but still smaller than the gas giants.
The planetary system where it resides consists of three celestial bodies orbiting a G-type star, which is a yellow dwarf similar to the Sun. Two of them are in orbits too close to their star, exposing them to extreme temperatures. Meanwhile, HD 20794 d is located in an area that astronomers refer to as the habitable zone.
Orbit and conditions on the planet
The trajectory of this planet is not perfectly circular—it moves in an elongated elliptical orbit. According to "National Geographic," this means it periodically enters the habitable zone and then exits it.
At the farthest point of its journey, it moves away from the star by 2 astronomical units (AU), while at the closest, it approaches 0.75 AU. For comparison, in the Solar System, a similar range covers Mars's orbit.
One complete orbit around the star takes 647 days, which is slightly shorter than a year on Mars. Depending on its position in the cycle, extreme conditions may prevail on the surface of HD 20794 d—from icy when it's farther from the star, to warmer when it approaches its inner edge.
Can life exist on HD 20794 d?
Scientists are still uncertain whether water exists on this super-Earth. If so, the water's state could change depending on the planet's position in the orbit—remaining mostly frozen but potentially melting and forming water bodies during its periodic entry into the habitable zone.
"National Geographic" explains that such a cycle could favor the development of simple life forms, although much depends on the atmospheric composition and surface temperatures.
The discovery of HD 20794 d was detailed in the prestigious journal "Astronomy & Astrophysics." Scientists analyzed data collected by advanced instruments, including the ESPRESSO and HARPS spectrographs.
For years, we analyzed data, carefully eliminating sources of contamination – said Michael Cretignier from Oxford, co-author of the research and the planet's discoverer.
Future studies of super-Earth
The proximity of the HD 20794 planetary system and its relatively bright star make this object a subject of intensive future research. New telescopes, such as the Extremely Large Telescope (ELT) in Chile, equipped with the ANDES spectrograph, will enable even more precise analyses of this exoplanet's atmosphere. This could allow astronomers to determine whether HD 20794 d indeed has conditions conducive to life.
