Barnard e is among the lightest planets ever found by the radial velocity method, which detects a planet from the small back-and-forth motion its gravity gives its star. Its minimum mass is about a fifth of Earth's. It is the outermost of four small planets now known around Barnard's Star, the closest single star to the Sun at about six light-years.
It was the hardest of the four to pin down. A team led by Jonay González Hernández first saw its signal, along with two others, in four years of measurements from the ESPRESSO spectrograph on the European Southern Observatory's Very Large Telescope, while confirming the first planet, Barnard b, in 2024. They said more observations were needed to confirm that these extra signals came from planets. In 2025 a team led by Ritvik Basant at the University of Chicago measured the star independently with MAROON-X on the Gemini North telescope. MAROON-X alone confirmed planets c and d; only when its data were combined with ESPRESSO's did the evidence for planet e become strong enough to confirm it.
Barnard e circles its star every 6.74 days at about 0.038 astronomical units, roughly a tenth of Mercury's distance from the Sun. Even though Barnard's Star is a dim red dwarf, that is still closer in than its habitable zone, the range of distances where liquid water could last on a surface. The habitable zone there begins further out, at orbits of about 10 days.
Much about it is unknown. None of the four planets has been seen crossing in front of the star, so their sizes and true masses have not been measured, only lower limits on the masses. The four are packed within about a week's orbit of the star, making this one of the most compact known systems around a small red dwarf. The 2025 data also rule out any planet heavier than about 0.57 Earth masses in the habitable zone itself, though a smaller one there could still be missed.