The solar system consists of our star, the sun, and everything bound to it by gravity: the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, along with dwarf planets like ...

It's an evocative idea that has long bedeviled scientists: a huge and mysterious planet is lurking in the darkness at the edge of our solar system, evading all our efforts to spot it. Some astronomers ...

In the cold, dark outskirts of planetary systems far beyond the reach of the known planets, mysterious gas giants and planetary masses silently orbit their stars — sometimes thousands of astronomical ...

Is there a massive undiscovered planet on the outer reaches of the solar system? The idea has been around since before the discovery of Pluto in the 1930s. Labeled as planet X, prominent astronomers ...

It used to be easy to know how many planets there were: nine. It had been nine planets for an entire generation before scientists started rethinking what counts as a planet. Pluto is out, but some ...

Rachel Feltman: For Scientific American’s Science Quickly, I’m Rachel Feltman. Unless you’re really on the low end of our listener age bell curve, chances are you grew up learning about our solar ...

Good news for those with a Pluto-shaped hole in their life, as astronomers may be on the verge of finding a new ninth planet in our solar system. The researchers—an international team led from ...

Does our solar system have a mysterious ninth planet? The discovery of a new dwarf world suggests not - Copyright AFP Eyad BABA Does our solar system have a ...