Scientists Discover Four Intriguing Planets Around Closest Single-Star Solar System to Earth

Astronomers have spotted four smaller-than-Earth exoplanets orbiting the closest single-star system to us, called Barnard's Star.

As detailed in a new paper published in the journal The Astrophysical Journal Letters, an international team of researchers discovered that the star — a small red dwarf star just 16 percent of our own Sun's mass and just under six light-years from Earth in the constellation Ophiuchus — has four tiny and seemingly rocky worlds orbiting it.

According to the astronomers, these exoplanets — which are among the smallest ever discovered — could force us to reevaluate our understanding of how planets form and evolve.

The four planets were spotted by the MAROON-X instrument, a highly sensitive piece of equipment attached to the Gemini North telescope at the International Gemini Observatory in Hilo, Hawaii.

"It’s a really exciting find — Barnard’s Star is our cosmic neighbor, and yet we know so little about it," said University of Chicago PhD student and first author Ritvik Basant in a statement. "It’s signaling a breakthrough with the precision of these new instruments from previous generations."

MAROON-X was specifically designed to detect tiny exoplanets orbiting red dwarf stars by detecting the minuscule back-and-forth motion of a star caused by the gravitational pull of orbiting planets, a trick scientists call the radial velocity technique.

Using the instrument, the team discovered four likely rocky exoplanets that are only anywhere from roughly 20 to 30 percent of the mass of Earth each. They orbit their star at an extremely close distance, completing a full revolution in a matter of a few Earth days.

The team also used data from a 2024 study, which involved the ESPRESSO instrument at the European Southern Observatory’s Very Large Telescope in Chile, to confirm the existence of one of the four exoplanets. Last year, astronomers detected an exoplanet with at least half the mass of Venus orbiting Barnard's Star.

"We observed at different times of night on different days," said Basant in the statement. "They’re in Chile; we’re in Hawai‘i. Our teams didn’t coordinate with each other at all. That gives us a lot of assurance that these aren’t phantoms in the data."

One of the four exoplanets spotted by MAROON-X was the smallest to have been discovered using the radial velocity technique, which could set the stage for many future discoveries like it.

Unfortunately, the planets are unlikely to harbor life since they're not in Barnard Star's habitable zone, the area around a star where temperatures allow liquid water to exist on a given planet's surface.

"With the current dataset, we can confidently rule out any planets more massive than 40 to 60 percent of Earth's mass near the inner and outer edges of the habitable zone," Basant told Space.com. "Additionally, we can exclude the presence of Earth-mass planets with orbital periods of up to a few years."

But that doesn't necessarily mean that will also be the case for other single-star systems like it. As our exoplanet detection methods continue to improve, astronomers are hoping to spot even more rocky worlds, which may still turn out to be habitable.

More on Barnard's Star: Astronomers Spot Mysterious Planet Orbiting the Closest Single Star

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