What happens when a visitor from another star system drops by? Join planetary astronomers Franck Marchis and Ariel Graykowski for a special SETI Live all about Comet 3I/ATLAS — only the third known interstellar object ever detected! Astronomers around the world, including citizen scientists in the Unistellar Network, are racing to learn as much as possible about this rare cosmic traveler. 3I/ATLAS is swinging through our neighborhood, reaching perihelion on October 30, 2025, just inside the orbit of Mars — a front-row seat for spacecraft like Lucy and Psyche. While it's currently hidden behind the Sun, it won't stay that way for long. By December 2025, 3I/ATLAS will reappear, ready for a fresh round of observations from Earth and its Lagrange-point observatories. We'll dive into what scientists have discovered so far, how they're studying this interstellar visitor, and what it might reveal about the chemistry and dynamics of other star systems. Don't miss it — interstellar comets don't come around every day! (Recorded live 31 October 2025.)