For a century, astronomers have been studying Barnard’s star in the hope of finding planets around it. First discovered by E.E. Barnard at Yerkes Observatory in 1916, it is the nearest single star system to Earth. Now, astronomers using the MAROON-X instrument on the Gemini North telescope, one half of NSF’s International Gemini Observatory, have found solid evidence for three exoplanets around Barnard’s star, two of which were previously classified as candidates. They’ve also combined data from MAROON-X with data from the ESPRESSO instrument on ESO’s Very Large Telescope to confirm the existence of a fourth planet, elevating it as well from candidate to bona fide exoplanet.
An artist’s illustration of exoplanets orbiting Barnard’s star. Image credit: International Gemini Observatory / NOIRLab / NSF / AURA / P. Marenfeld.
Barnard’s star is an M3.5-type star located in the constellation of Ophiuchus.
At nearly 6 light-years away, it is the next closest star to the Sun after the Alpha Centauri triple stellar system.
Otherwise known as Gliese 699 or GJ 699, Barnard’s star is thought to be 10 billion years old due to its slow rotation and low levels of activity.
According to the new study, the star hosts at least four planets, each only about 20 to 30% the mass of Earth.
They are so close to their home star that they zip around the entire star in a matter of days.
That probably means they are too hot to be habitable, but the find is a new benchmark for discovering smaller planets around nearby stars.
“It’s a really exciting find — Barnard’s star is our cosmic neighbor, and yet we know so little about it,” said Ritvik Basant, a Ph.D. student at the University of Chicago.
“It’s signaling a breakthrough with the precision of these new instruments from previous generations.”
Because stars are so much brighter than their planets, it’s easier to look for effects that planets have on their stars — like monitoring the wind by watching how a flag moves.
The MAROON-X instrument looks for one such effect; the gravity of each planet tugs slightly on the star’s position, meaning the star seems to wobble back and forth.
MAROON-X measures the color of the light so precisely that it can pick up these minor shifts, and even tease apart the number and masses of the planets that must be circling the star to have this effect.
Basant and colleagues rigorously calibrated and analyzed data taken during 112 different nights over a period of three years.
They found solid evidence for three planets around Barnard’s star.
When the team combined their findings with data from the ESPRESSO instrument, they saw good evidence for a fourth planet.
“These planets are likely rocky planets, rather than gas planets like Jupiter,” the astronomers said.
“That will be difficult to pin down with certainty; the angle we see them from Earth means we can’t watch them cross in front of their star, which is the usual method to find out if a planet is rocky.”
“But by gathering information about similar planets around other stars, we can make better guesses about their makeup.”
The team’s findings were published today in the Astrophysical Journal Letters.
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Ritvik Basant et al. 2025. Four Sub-Earth Planets Orbiting Barnard’s Star from MAROON-X and ESPRESSO. ApJL 982, L1; doi: 10.3847/2041-8213/adb8d5
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