Free Astronomy Magazine May-June 2025

6 MAY-JUNE 2025 ASTRO PUBLISHING S cientists Andreas Seifahrt (left) and Jacob Bean (right) unpack the MAROON-X instrument for installation on the Gemini North telescope, one half of the Inter- national Gemini Observatory, funded in part by the U.S. National Science Founda- tion and operated by NSF NOIRLab, in 2019. [International Gemini Observatory/ NOIRLab/NSF/AURA/J. Bean] Earth, the planets do not cross in front of their star, which is the usual method for determining a planet’s composition. But with information from similar planets around other stars, the team will be able to make better estimates of their makeup. T his animation shows the orbital dynamics of the Barnard’s Star planetary system. For a century, astronomers have been studying Barnard’s Star in the hope of finding planets around it. First discovered by E. E. Barnard at Yerkes Observa- tory in 1916, it is the nearest single star system to Earth. Now, using in part the Gemini North telescope, one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation and operated by NSF NOIR- Lab, astronomers have discovered four sub-Earth exoplanets orbiting the star. One of the planets is the least massive exo- planet ever discovered using the radial velocity technique, indicating a new benchmark for discovering smaller planets around nearby stars. [International Gemini Observatory/NOIRLab/NSF/AURA/R. Proctor/J. Pollard] thor of the paper appearing in The Astrophysical Journal Letters . “It’s signaling a breakthrough with the precision of these new instruments from previous generations.” The newly discovered planets are most likely rocky planets, rather than gas planets like Jupiter. How- ever, this will be difficult to pin down with certainty since, because of the angle we observe them from They were, however, able to rule out with a fair degree of certainty the existence of other exoplanets with masses comparable to Earth in Barnard Star’s habitable zone — the region of space around a star that is just right to allow liquid water on an orbiting planet’s surface. Barnard’s Star has been called the