Billions of years ago, while the solar system was still young, a massive object may have drifted into it. It's not a spaceship, but it is an alien visitor in its own right—a colossal interstellar body ...

One million alien visitors from another star system could already be lurking in the solar system. We aren't talking about "little green men" here, however — more "little (and not so little) gray rocks ...

There’s a visitor in town, and its name is 3I/ATLAS. The presumed interstellar comet presents a rare opportunity for astronomers to study an object born a long time ago in a star system far, far away.