On July 1, 2025, the Asteroid Terrestrial-impact Last Alert System (ATLAS) did its job superbly and spotted a sizeable object as it hurtled its way through the Solar System, 670 million kilometers (410 million miles) from the Sun. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

By studying the object's trajectory, it was soon confirmed to be an interstellar object, meaning an object that originated from outside the Solar System. How do we know?

"Kepler was the first to realize that the orbits of planets are elliptical, with the Sun sitting in a special position known as the focus. Every ellipse has two foci. Ellipses have another important parameter called eccentricity. Eccentricity of zero means a circle where the two foci are in a s

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