# Astronomers may have discovered the first exomoon A giant natural satellite found outside our Solar System - **Source:** [Hacker News (news.ycombinator.com)](https://brifing.si/source/13c923cd-6d99-442b-9b8b-1181f4d8cd91) - **Published:** 2026-07-23 - **Topic:** [Business](https://brifing.si/c/business) - **Original article:** - **On Brifing:** https://brifing.si/s/5f23a5e7-fcc1-4c82-8de1-7c22a76fee87 ## Historic discovery The European Southern Observatory's Very Large Telescope has detected the first natural satellite candidate outside our Solar System. This massive celestial body in the CD-35 2722 system challenges traditional definitions of a 'moon'. ## Unusual system The discovered exomoon orbits a brown dwarf. The largest object in the system is the star CD-35 2722, which has about half the mass of the Sun. This configuration is forcing astronomers to rethink terminology. ## Definition dilemma This celestial body, larger than Jupiter, technically qualifies as a planet in size. However, its orbit around a brown dwarf rather than a star creates a tendency to call it a 'moon'. ## Discovery method The team applied the radial velocity method used to find the first exoplanet around a Sun-like star. By measuring small wobbles in the brown dwarf's motion, they detected evidence of the exomoon. ## Scientific significance This discovery could expand our understanding of celestial body formation and evolution. The diversity of satellites in different systems will help us comprehend universal dynamics. ## Terminology debate Astronomers note that such discoveries challenge traditional definitions of 'planet' and 'moon'. Significant differences between systems may require new categories. ## Previous candidates Despite the discovery of over 6000 exoplanets to date, only a few exomoon candidates have been identified. None had evidence as strong as this discovery. ## Technical details Using ESO's CRIRES+ instrument, the team measured slight orbital variations of the brown dwarf. The data strongly supports the existence of a giant satellite. ## Comparison Unlike the small, rocky moons in our Solar System, this exomoon is the size of a gas giant. This difference shows the diversity in celestial body formation processes. ## Future research ESO's upcoming Extremely Large Telescope will be able to detect smaller exomoons. This will help astronomers better understand system diversity in the universe. ## Team perspective Lead researcher Kevin Hoy describes this system as 'super weird'. Team member Alice Zurlo emphasizes that the discovery is a milestone requiring us to rethink terminology. ## Scientific impact Published in Nature, this discovery has created great excitement in the astronomy community. Confirmation of exomoons' existence could open a new chapter in our understanding of the universe. ## Sources covering this story - https://www.eso.org/public/news/eso2610/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._