The small exoplanets of our Sun’s second-nearest neighbor, Barnard’s Star, are inhospitable wastelands, British astronomers say.
Located six light-years from Earth, Barnard’s Star is separated from our closest neighbor, Alpha Centauri, by about 66° in our sky. Now, University of Cambridge researchers have revealed their findings on this exosolar system in a recent paper published in the Monthly Notices of the Royal Astronomical Society.
After careful analysis, the astronomers announced that the exoplanets are unlike any in our solar system, presenting a brutal and barren environment.
Barnard’s Star Exoplanets
Scientists only discovered these four small planets orbiting Barnard’s Star in 2025. Unlike anything in our solar system, these orbital bodies fit into a size range larger than Mars, but smaller than Earth or Venus.
Like a peeled onion, these smaller planets are rich in a mineral only found deep below the Earth’s surface. Chemical analysis revealed large amounts of the mineral periclase on the surface of these planets, something typically only found hundreds of kilometers deep on our planet.
“Barnard’s Star has an enormous amount of the element magnesium compared to other stars, so its planets are likely to be rich in magnesium too,” said lead author Xander Byrne from Cambridge’s Institute of Astronomy. “On Earth, that magnesium goes into making minerals called olivines, which are really important for storing water within the planet.”
A Lack of Water and Atmosphere
Unfortunately for those looking for extraterrestrial life, magnesium serves a different purpose on these exoplanets. Instead of water-storing olivine, it produces the abundant periclase, which is a poor store of water.
Even worse, these inhospitable exoplanets likely no longer have an atmosphere. According to the University of Cambridge team, these ten-billion-year-old planets probably only managed to hold an atmosphere for two billion years at most.
“These planets were always going to be hostile, because they’re really close to their star,” said Byrne. “Even the outermost planet orbits ten times closer than Mercury orbits the Sun. When you’re that close to your star, and have such little gravity, your atmosphere just gets blown off.”
In addition to the lack of atmosphere, the planets’ proximity to Barnard’s Star leaves them tidally locked, like our Moon, with one side always facing toward the star.
Exoplanet Stability
However, there is one positive element to these small planets. Typically, such close-orbiting systems are highly unstable, with the planets shooting out from the system, falling into their host star, or catastrophically colliding. Yet in this case, the system is as ordered as a piece of music.
The three inner planets of the exosolar system have years in a 9:12:16 ratio, producing two of what is known as a “perfect fourth” in music. This musical harmony is known as an orbital resonance, with the same type of effect stabilizing Jupiter’s moons in their orbits around that planet.
While our ability to view Barnard’s Star from Earth may be limited, the European Space Agency’s upcoming Plato mission may allow astronomers to discover ever smaller worlds orbiting in the nearby exosolar system.
“Larger planets are much easier to detect than small ones, so we know about very few sub-Earth planets like the ones in this system,” said Byrne. “But the sensitivity of these new missions will help to reduce this bias, allowing us to discover more and more planets that are small and rocky, like Earth.”
The true significance of the research may lie in the value of a null result. While these planets are bleakly hostile to life, observing this exosolar system’s composition can aid future astronomers in narrowing down the search for extraterrestrial life.
The paper, “The Barnard’s Star Planetary System: Stability, Composition, and Evolution of Four Sub-Earth Exoplanets,” appeared in Monthly Notices of the Royal Astronomical Society on June 24, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.