Astronomers detailed 3I/ATLAS, a rare interstellar comet traveling more than 124,000 miles per hour, highlighting its value for understanding planet formation. The interstellar comet 3I/ATLAS follows a hyperbolic orbit (eccentricity ~6.1), confirming a brief solar system passage. First spotted July 1, 2025 by an ATLAS telescope in Chile, it showed non-gravitational acceleration and rapid brightening near the Sun in late October. With a core about 3.4 miles wide, it shifted from red to blue and passed Earth at roughly 167 million miles on December 19, 2025. International teams, NASA, and ESA reported a high carbon dioxide–to–water ratio; NASA’s Charles Lisse called it “well baked.” Officials noted no Earth threat. Data from ESA’s JUICE are expected in early 2026.
