The solid innermost core is likely composed of iron and nickel, the same ingredients as Earth's, but quite possibly also ...

Astronomers have been scouring the outer solar system for signs of a hypothetical ninth planet for almost a decade, without success. However, we may finally be on the cusp of finding it, experts say.

When the Sun expands into a red giant, it will swallow the inner solar system and raise the temperature in the outer regions.