Astronomers Discover a Small Exoplanet That’s Our Cosmic Neighbor at Just Six Light-Years Away

Astronomers have discovered a new exoplanet that orbits a red dwarf star “just” six light-years away from Earth. Barnard’s star is the closest solo star and the second-closest stellar system to our planet, which is why experts were searching for Earth-like worlds in its proximity. But before you get excited—no, the exoplanet, called Barnard b, is not habitable.

The scientists’ findings, which were made with the European Southern Observatory’s Very Large Telescope at the Paranal Observatory in Chile, were published in the journal Astronomy and Astrophysics on Tuesday. Their conclusions are based on more than four years of observations.

“Even if it took a long time, we were always confident that we could find something,” lead author Jonay González Hernández, a researcher at the Institute of Astrophysics of the Canary Islands in Spain, says in a statement.

Astronomically speaking, Barnard’s star is in “our backyard,” per Forbes’ Jamie Carter—but that’s not the only reason scientists were searching in its region. Low-mass rocky planets are easier to spot around smaller—and thus dimmer—red dwarf stars like Barnard’s star, compared to around larger stars like our sun, making them ideal locations for exoplanet hunting.

The team discovered Barnard b by analyzing how much Barnard’s star “wobbled” in response to the planet’s gravitational pull. They used an instrument called ESPRESSO to measure these subtle movements, and the findings were repeated with other specialized instruments as well.

“It took us quite long to detect this tiny planet, since the planet signal is quite weak and very difficult to detect,” González Hernández tells Newsweek’s Jess Thomson.

That tiny planet has at least half the mass of Venus and completes one orbit around Barnard’s star in a mere 3.15 Earth days. It charts its path around the red dwarf at a distance of 1.8 million miles, which is only 5 percent of the distance between the sun and Mercury, the innermost planet in our solar system. So, even though Barnard’s star is 80 percent smaller than our sun and has half its surface temperature at 5,000 degrees Fahrenheit, its planet’s surface temperature is scorching hot—roughly 257 degrees Fahrenheit—because of its proximity to the star.

“Barnard b is one of the lowest-mass exoplanets known and one of the few known with a mass less than that of Earth. But the planet is too close to the host star, closer than the habitable zone,” says González Hernández in the statement. “Even if the star is about 2500 degrees [Celsius] cooler than our sun, it is too hot there to maintain liquid water on the surface.”

In other words, Barnard b is outside of its host star’s so-called “habitable zone”—the region surrounding a star with temperatures that allow for liquid water, and potentially life, on the surface of an exoplanet. Astrobiologists call that sweet spot the “Goldilocks zone”—it’s not too hot and not too cold.

Astronomers have been searching for exoplanets in proximity to Barnard’s star since the 1960s, Alex Wilkins reports for New Scientist. In 2018, researchers suggested they’d finally found one. The signals they interpreted to be an exoplanet at least three times bigger than Earth, however, were actually traced to increased stellar activity—and the disproved claim joined a long list of false positive exoplanet discoveries around Barnard’s star, per Mashable’s Elisha Sauers

“These are very tricky detections, and it’s always hard because you have the activity of the star, the stellar magnetic fields, which are rotating with the star,” Rodrigo Fernando Díaz, a researcher at the National University of San Martín in Argentina who wasn’t involved in the study, tells New Scientist.

Speaking of tricky detections, the scientists also found hints of three more exoplanets that might also be orbiting Barnard’s star, but further observations will be needed to confirm them.

“Let’s see what happens in the next years,” González Hernández tells Newsweek. “These signals point to an additional three planets that are also less massive than the Earth. All of them are closer to the habitable zone.”

Margherita Bassi | READ MORE

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.