Astronomers now have their most detailed view yet of a captivating group of small planets orbiting Barnard’s Star, one of the closest stars to our Sun. These worlds are unusual, rocky, and almost certainly incapable of supporting life.
Barnard’s Star is less than six light-years away, making it the nearest neighbor after the Alpha Centauri system. In 2025, scientists detected four planets circling the star. All are smaller than Earth and Venus but larger than Mars, placing them in a size category with no counterparts in our solar system.
Researchers from the University of Cambridge have now examined the star’s chemical makeup to infer what its planets might consist of. Since stars and their planets form from the same material, the elements present in the star can give important clues about their planetary compositions.
They found that Barnard’s Star contains notably high amounts of magnesium. This indicates its planets are probably also rich in magnesium. On Earth, much of our magnesium is stored in olivine minerals, which are capable of holding water deep beneath the surface—potentially playing a role in Earth’s long-term water cycle.
However, the planets around Barnard’s Star are likely quite different. Their high magnesium content probably results in the formation of large amounts of a mineral called periclase. Unlike olivine, which can trap water and is found near the surface on Earth, periclase is mostly located deep underground and is less effective at water storage.
Adding to their harsh environment, the planets probably lack significant atmospheres. They orbit extremely close to Barnard’s Star—so near that even the outermost planet is about ten times closer than Mercury is to the Sun. This proximity, combined with their weak gravitational pull, suggests that radiation and stellar particles could have gradually stripped away any original atmospheres.
It’s estimated that these atmospheres last no longer than about two billion years. Given that Barnard’s Star is roughly 10 billion years old, these planets might have been airless for most of their existence. They are also likely tidally locked, meaning one side always faces the star while the other remains in endless darkness—similar to how the Moon always shows the same face to Earth.
Remarkably, despite these extreme conditions, the planets maintain stable orbits. The inner three planets are arranged in a resonance pattern with orbital periods in a 9:12:16 ratio, which may help keep their paths stable over time.
Upcoming missions, like the European Space Agency’s Plato, are expected to discover many more small rocky planets like these. Although the worlds surrounding Barnard’s Star are probably uninhabitable, studying them offers valuable insights into what conditions might enable or prevent life on other planets, based on the star’s characteristics, planetary composition, and environmental dynamics.
Source: KSR.