Barnard’s Star, a red dwarf located about six light years from Earth, is the closest single star to our solar system. Much smaller and less luminous than the Sun, red dwarfs are the smallest type of regular stars. Scientists, eager to study nearby potentially habitable planets, are excited by the recent discovery of the first confirmed planet orbiting Barnard’s Star: a rocky exoplanet named Barnard b.
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Barnard b has a mass approximately 40% that of Earth and an estimated diameter of around 9,700 kilometres, about three-quarters of Earth’s size. Despite this, its surface temperature of 125°C makes it inhospitable for life. The planet orbits Barnard’s Star very closely, completing a revolution in just three Earth days. It is situated 20 times closer to its star than Mercury is to the Sun. This proximity, combined with the star’s faint luminosity, results in an extreme environment unsuitable for life as we know it.
However, the excitement doesn’t stop with Barnard b. Researchers have identified “strong hints” of three other potential planets orbiting Barnard’s Star. These planets, if confirmed, are smaller than Earth, with masses ranging from 20% to 30% of our planet’s. The hope is that at least one of them might reside within the star’s habitable zone, where conditions could allow liquid water to exist on the surface, making them more promising candidates for life.
This discovery was made using the Espresso instrument on the European Southern Observatory’s Very Large Telescope in Chile. If these additional planets are confirmed, Barnard’s Star would host the only known multi-planet system entirely made up of planets smaller than Earth.
Barnard’s Star, located in the constellation Ophiuchus, is roughly 16% the mass of the Sun and has a diameter about 19% of it. It’s also far less hot and much older, estimated to be over twice the Sun’s age. Despite being cold and faint, Barnard’s Star is a relatively quiet star compared to other red dwarfs, which are prone to frequent flaring.
The proximity of Barnard’s Star makes it an ideal target for further study. Red dwarfs are the most common type of star in the Milky Way galaxy, and it’s easier to detect low-mass rocky planets orbiting them compared to larger stars. Only the three stars in the Alpha Centauri system, about four light years away, are closer to our solar system than Barnard’s Star.
Two exoplanets have already been discovered in the Alpha Centauri system, orbiting the red dwarf Proxima Centauri. One has a mass roughly equal to Earth’s, while the other is about 25% of Earth’s mass. While interstellar travel remains beyond current human technology, projects like Breakthrough Starshot are exploring the possibility of reaching nearby stars like Barnard’s Star and Alpha Centauri. If successful, these systems could be among the first destinations for future space exploration.
“While they are close in astronomical terms, they are currently out of reach,” said astronomer Alejandro Suárez Mascareño. “However, they are likely targets for any future interstellar missions.”
