Scientists Discover ‘Super Earth’ That Orbits Its Star In 647 Days

A new "super-Earth" planet has been discovered orbiting a star just 20 light-years away from Earth, offering exciting possibilities for future research into potentially habitable worlds. The planet, the outermost of three detected around the star HD 20794, has a 647-day orbit, which is similar to Mars in our solar system. However, its orbit is highly eccentric, meaning it follows an oval shape, which causes extreme temperature changes.

The planet experiences a dramatic temperature cycle. As it orbits its star, it moves close enough at one point to experience extreme heat, similar to Venus’s temperature. But at its farthest point, the planet is nearly twice the distance from Earth to the Sun, causing temperatures to drop low enough to freeze any potential water. These temperature changes occur about every 300 days, likely for billions of years.

A Habitable Zone with Unique Conditions

For a portion of its orbit, the planet is in the "habitable zone" the area around a star where conditions are right for liquid water to exist. However, because of its elliptical orbit, the planet swings in and out of the habitable zone, bringing it too close to the star at one point, and too far at another. Despite these extremes, the planet could still be rocky, like Earth, but possibly much heavier around six times the mass of Earth.

A Star System

The star HD 20794 and its planets have been under study for years. The team of international astronomers, led by Nicola Nari of Light Bridges S.L. and the Instituto de Astrofisica de Canarias, used data from precision instruments in Chile to confirm the planet’s presence. These instruments, HARPS and ESPRESSO, measure tiny changes in the light from the star caused by the gravitational pull of planets as they orbit.

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The discovery of this super-Earth makes the HD 20794 system an exciting target for future space-based telescopes. NASA’s Habitable Worlds Observatory, once launched, will study the atmospheres of planets like this to look for signs of life. Given its proximity, only 20 light-years away, and its relatively quiet star, this system is ideal for further research.

The Team Behind the Discovery

The groundbreaking research was led by Nicola Nari, with Dr. Michael Cretignier of the University of Oxford, who first identified the planet’s signal in 2022. Their findings were published in January 2025 in Astronomy and Astrophysics.