Barnard’s Star is one of the brightest stars in our night sky for astronomers because of its proximity to Earth. Situated just under six light-years away, it ranks as the second-closest star system after Alpha Centauri. In 2025, researchers confirmed the presence of four small planets orbiting this nearby star.
A recent study has provided the clearest view yet of these unusual worlds, revealing that they are rocky, incredibly hostile, and markedly different from any planets in our solar system. Published in the Monthly Notices of the Royal Astronomical Society, the study was led by scientists from the University of Cambridge. By analyzing the star’s chemical composition, the team estimated what these planets might be made of and how they have changed over billions of years.
All four planets are smaller than Earth and Venus but larger than Mars. Interestingly, this size range is quite common in other planetary systems, even though our solar system lacks planets of this size. As more small rocky worlds are discovered, scientists are beginning to realize that our solar system may not be as typical as previously thought.
One of the most surprising discoveries is that these planets are possibly rich in a mineral called periclase. On Earth, periclase is found deep underground, hundreds of kilometers below the surface. Barnard’s Star has a much higher magnesium content compared to the Sun, which likely influenced the mineral formation inside its planets. On Earth, magnesium is mainly stored in olivine minerals that help retain water. However, the high magnesium levels around Barnard’s Star probably led to the formation of more periclase, which isn’t as efficient at holding water. This suggests that these planets might have had significantly less water from the start.
The planets orbit very close to their star. The farthest one circles Barnard’s Star at about ten times the distance Mercury orbits the Sun. Such proximity to the star likely caused intense radiation that stripped away any original atmospheres, which probably only lasted for around two billion years—considerably shorter than the star’s estimated age of around ten billion years.
Because of their tight orbits, the planets are expected to be tidally locked, meaning one side constantly faces the star while the other remains in perpetual darkness, similar to how the Moon always shows one face to Earth.
Despite their close proximity, the planets seem to maintain stable orbits. The inner three move in a resonant pattern, with their orbital periods following a 9:12:16 ratio. Gravitational interactions like this are similar to those that keep some of Jupiter’s moons in stable orbits, possibly preventing the planets from colliding.
While these worlds are almost certainly inhospitable, the findings offer valuable insights into planetary formation around different types of stars. Upcoming space missions, including the European Space Agency’s PLATO, aim to find many more small rocky planets like these. By studying the chemistry of stars and their planets, astronomers hope to better identify which distant worlds might support life.