A recent analysis reveals that four exoplanets orbiting Barnard’s Star, the closest single star to our Sun, are likely rich in the mineral periclase, which contributes to their hostile environments, making them incapable of supporting life.
Artist’s impression of an exoplanet orbiting Barnard’s Star. Image credit: International Gemini Observatory / NOIRLab / NSF / AURA / P. Marenfeld.
Barnard’s Star, a 10 billion-year-old red dwarf, is located just 6 light-years from Earth in the constellation Ophiuchus.
Also known as Gliese 699 or GJ 699, it ranks as the second closest star to the Sun, following the Alpha Centauri triple star system.
In 2025, astronomers discovered four rocky planets orbiting this star, each smaller than Earth and Venus but larger than Mars.
Through a detailed analysis of Barnard’s Star’s chemical composition, astronomer Xander Byrne and his team at the University of Cambridge found that the planets are abundant in a rare mineral called periclase, typically found a few hundred kilometers beneath Earth’s surface.
“Barnard’s Star has elevated magnesium levels compared to other stars, suggesting that its planets also contain significant magnesium,” Byrne noted.
“On Earth, magnesium contributes to the formation of olivine, a crucial mineral for water storage underground.”
However, the high magnesium content leads to the formation of periclase, which retains little to no water.
Compounding the issue, the planets around Barnard’s Star are unlikely to have atmospheres.
“These planets face hostile conditions due to their proximity to the star,” Dr. Byrne explained.
“Even the furthest planets orbit ten times closer than Mercury orbits the Sun.”
“At such close range and with low gravity, any atmosphere is easily stripped away.”
These exoplanets may have preserved an atmosphere for a maximum of 2 billion years, a brief duration compared to the system’s estimated 10 billion-year age.
The proximity to Barnard’s Star also imposes unique effects on the planets. Researchers found that all four are tidally locked, similar to how the Moon presents only one face to Earth.
This results in one hemisphere of each planet being perpetually bathed in sunlight while the other remains in darkness.
Compact planetary systems like Barnard’s Star are often unstable, with gravitational interactions potentially leading to collisions, falls into the star, or ejections from the system.
However, phenomena like orbital resonance appear to stabilize the planets around Barnard’s Star.
The orbital durations of the three inner planets are in a 9:12:16 ratio, reminiscent of two consecutive perfect fourths in music.
This harmonic relationship may help stabilize their orbits, shielding the Barnard system from disruptive gravitational forces.
Future missions, such as ESA’s Plato mission, aim to uncover more small planets similar to those surrounding Barnard’s Star.
“Larger planets are easier to detect than smaller ones, which leaves a gap in our knowledge about such exoplanets,” Dr. Byrne remarked.
“The enhanced sensitivity of these new missions will help address this bias, enabling us to discover more small, rocky planets akin to Earth.”
The team’s paper was published in the June 24th issue of Royal Astronomical Society Monthly Notices.
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Xander Byrne et al. 2026. Barnard’s Planetary System: Stability, Composition, and Evolution of Four Exoplanets. MNRAS 550 (2): stag1207; doi: 10.1093/mnras/stag1207
Source: www.sci.news
