Our Smallest Neighbors
Astronomers have confirmed the existence of four exoplanets orbiting Barnard’s Star, the closest single star to Earth, following decades of false leads. These small, rocky worlds—previously undetectable with older instruments—were identified using the radial velocity method, which tracks the subtle “wobbles” in a star’s movement caused by an orbiting planet’s gravitational pull. Barnard’s Star, a red dwarf just six light-years away, has been a prime target for exoplanet searches for over 50 years, but traditional methods, like detecting dips in starlight, failed due to the planets’ tiny size.
“It’s a really exciting find—Barnard’s Star is our cosmic neighbor, and yet we know so little about it,” said lead study author Ritvik Basant, a doctoral student at the University of Chicago. The newly discovered planets, classified as sub-Earths, range from 19% to 34% of Earth’s mass and have incredibly tight orbits, all within the distance of Mercury’s orbit around the Sun. The closest completes a full orbit in just three days, while the farthest takes seven. They were detected using the MAROON-X instrument on Hawaii’s Gemini North telescope, which offers the precision needed to spot such small planetary signals.
Although these planets are likely barren, exposed to intense radiation and stripped of any atmosphere or water, their discovery provides valuable insights into planetary formation. Sub-Earths like these may have a broader range of compositions than larger exoplanets, offering fresh perspectives on the diversity of planets in our galaxy. The findings, published in Astrophysical Journal Letters, mark a significant step forward in understanding the hidden worlds orbiting nearby stars.