Astronomers have made a groundbreaking discovery, uncovering four tiny exoplanets orbiting Barnard’s Star, the nearest single star system to Earth. The sub-Earth planets, each about 19% to 34% the mass of our planet, are classified as “sub-Earths” due to their size and composition.
The discovery was made using a new instrument called MAROON-X, mounted on the Gemini North telescope in Hawaii. This instrument detects the subtle wobble of stars caused by the gravity of orbiting planets, known as the radial velocity technique. The team spotted the least massive exoplanet ever found, which they hope will lead to the discovery of more sub-Earth exoplanets.
The four tiny worlds are so small that they’re comparable to Mars, with orbits that zip around their stellar host in a matter of days. However, due to their proximity to the star, their surfaces are likely too hot to be habitable. This means they’re not within the habitable zone of Barnard’s Star, where liquid water can exist on their surface.
The discovery is significant because planets of this size are largely unexplored beyond our solar system. The findings suggest that smaller exoplanets may be more varied in composition than larger ones, which could lead to a new understanding of how planets form and potentially open up the possibility of habitable worlds.
This breakthrough comes after decades of searching for evidence of planets orbiting Barnard’s Star. The team used data from 112 nights spanning three years to confirm the existence of four exoplanets, including two previously suggested candidates. The combined dataset revealed evidence for a fourth planet, which has sparked excitement among astronomers.
The discovery highlights the power of next-generation instruments like MAROON-X and ESPRESSO, which have significantly improved our ability to detect sub-Earth mass planets. The team’s findings are a testament to the precision and accuracy of these new tools, unlocking new possibilities for understanding the universe.
Source: https://edition.cnn.com/2025/03/17/science/barnards-star-exoplanets/index.html