At number 9️⃣ of our #UNOOSATop10 highlights, a landmark moment for planetary defence: the first time ever that the International Asteroid Warning Network (IAWN) issued an official warning. ☄️🔭 At the very beginning of 2025, asteroid 2024 YR4 briefly passed the 1% impact probability threshold for notification, prompting IAWN to alert UNOOSA so that we could inform Member States and coordinate next steps. Although follow-up observations confirmed the asteroid posed no threat, the case marked a first successful testing of global communication channels and demonstrated why international cooperation is essential to prepare for high-impact risks. 🌌Astronomers also focused on Comet 3I/ATLAS, only the third interstellar object ever detected. Though harmless, its unique path offered a rare scientific opportunity, prompting IAWN to launch a global observing exercise to refine astrometry methods from comet observations. IAWN, coordinated through nasa's Planetary Defense Coordination Office...