Planetary system discovered around Barnard's Star

Planetary system discovered around Barnard's Star
by Clarence Oxford
Los Angeles CA (SPX) Mar 13, 2025

For over a century, astronomers have been intrigued by Barnard's Star, the closest single-star system to Earth, in their quest to identify planetary bodies orbiting it. Initially observed in 1916 by E. E. Barnard at Yerkes Observatory, this red dwarf has long been a target for exoplanet research. Red dwarfs are known for their propensity to host compact planetary systems, often composed of multiple rocky planets, making them key objects of study in exoplanetary science.

A significant breakthrough has been made by a research team led by Jacob Bean from the University of Chicago. Their specialized instrument, MAROON-X, designed explicitly for detecting exoplanets around red dwarfs, has confirmed the presence of multiple planets around Barnard's Star. MAROON-X is installed on the Gemini North telescope, part of the International Gemini Observatory, which is funded in part by the U.S. National Science Foundation and operated by NSF NOIRLab.

MAROON-X utilizes the radial velocity technique, which identifies minuscule shifts in a star's light spectrum caused by the gravitational tug of orbiting planets. This allows scientists to determine the number and masses of planets influencing the star's motion with remarkable precision.

After analyzing data collected over 112 nights across three years, the research team confirmed the existence of three exoplanets, two of which were previously classified as candidates. Additionally, by integrating data from the ESPRESSO instrument on the European Southern Observatory's Very Large Telescope, a fourth planet was also confirmed, advancing it from a candidate status to a confirmed exoplanet.

"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 PhD student at the University of Chicago and lead author of the study published in *The Astrophysical Journal Letters*. "It's signaling a breakthrough with the precision of these new instruments from previous generations."

The newly confirmed exoplanets are likely rocky rather than gaseous like Jupiter. However, since they do not transit in front of their star from Earth's vantage point, determining their exact compositions remains challenging. Nonetheless, insights from similar planetary systems can provide reasonable estimates regarding their makeup.

Furthermore, the study has ruled out the presence of Earth-mass planets in Barnard's Star's habitable zone, the region where conditions might allow liquid water to exist. The confirmation of these planets brings new credibility to exoplanet research around this star, which has been the subject of various disputed planetary claims over the years.

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

These four exoplanets, each only 20 to 30% the mass of Earth, orbit Barnard's Star in just a few days. Notably, the fourth planet is the smallest ever detected using the radial velocity method. This breakthrough raises hopes for discovering more sub-Earth-sized planets in the future.

While most rocky planets detected so far tend to be significantly larger than Earth and share many commonalities, smaller exoplanets could exhibit a broader range of compositions. Expanding the catalog of such worlds will help scientists unravel the diversity of planetary formation and the factors that contribute to potentially habitable environments.

"The U.S. National Science Foundation is collaborating with the astronomy community on an adventure to look deeper into the Universe to detect planets with environments that might resemble Earth's," said Martin Still, NSF program director for the International Gemini Observatory. "The planet discoveries provided by MAROON-X mounted on Gemini North provide a significant step along that journey."

Currently, MAROON-X remains a visiting instrument at Gemini North. However, due to its exceptional performance and strong demand from researchers, it is in the process of being transitioned into a permanent facility instrument.

"This result demonstrates the competitive, state-of-the-art capabilities that Gemini offers its user community. The observatory is in the middle of rejuvenating its instrumentation portfolio and MAROON-X is part of the first wave of new instruments, alongside GHOST on Gemini South and IGRINS-2 on Gemini North," stated Andreas Seifahrt, Associate Director of Development for the International Gemini Observatory, co-author of the paper, and a key figure in the design and construction of MAROON-X.

Research Report:Four sub-Earth planets orbiting Barnard's Star from MAROON-X and ESPRESSO