Barnard’s Star is one of the most famous stars in the night sky for astronomers because it is so close to Earth.
Located just under six light-years away, it is the second-closest star system after Alpha Centauri.
In 2025, scientists confirmed that four small planets orbit this nearby star.
Now, a new study has revealed the clearest picture yet of these unusual worlds, showing that they are rocky, extremely hostile, and very different from any planet in our own solar system.
The research, published in the Monthly Notices of the Royal Astronomical Society, was led by scientists at the University of Cambridge.
By studying the chemical makeup of Barnard’s Star, the team was able to estimate what its planets are likely made of and how they have evolved over billions of years.
The four planets are all smaller than Earth and Venus but larger than Mars. This size is surprisingly common in other planetary systems, even though our own solar system has no planets in this range.
As scientists discover more of these small rocky worlds, they are learning that our solar system may not be as typical as once thought.
One of the most surprising findings is that these planets are probably rich in a mineral called periclase. On Earth, periclase exists only deep beneath the surface, hundreds of kilometers underground. Barnard’s Star contains much more magnesium than the Sun, and that extra magnesium likely changed the way minerals formed inside its planets.
On Earth, magnesium is mostly found in minerals called olivines, which help store water inside the planet. Around Barnard’s Star, however, the large amount of magnesium likely produced much more periclase instead. Because periclase is not as good at holding water, these planets may have had much less water available from the beginning.
The planets also orbit incredibly close to their star. Even the most distant one circles Barnard’s Star about ten times closer than Mercury orbits the Sun. At such close distances, the star’s radiation would have stripped away any atmospheres the planets may once have had. The researchers estimate that any atmosphere could have survived for no more than about two billion years, far shorter than the star’s estimated age of around ten billion years.
Another result of these tight orbits is that the planets are likely tidally locked. This means one side of each planet always faces the star, while the other side remains in permanent darkness, much like the Moon always shows the same face to Earth.
Despite being packed closely together, the planets appear to have stable orbits. The researchers found that the inner three planets move in a repeating pattern known as orbital resonance, with their orbital periods following a 9:12:16 ratio. Similar gravitational patterns help keep some of Jupiter’s moons in stable orbits and may be preventing these planets from crashing into one another.
Although these nearby worlds are almost certainly uninhabitable, the study provides valuable clues about how planets form around different types of stars. Future space missions, including the European Space Agency’s PLATO mission, are expected to discover many more small rocky planets like these.
By comparing the chemistry of stars with the planets that orbit them, astronomers hope to better identify which distant worlds might have the right conditions to support life.
Source: KSR.
