The number of planets that orbit the sun depends on what you mean by “planet,” and that’s not so easy to define ...

A new study suggests that a close encounter with a massive interstellar object, possibly eight times the mass of Jupiter, may have significantly altered the orbits of the four outer planets in our ...

Aside from the solar system once again having nine planets ... “We would need to refine the definition of a planet since an Earth-like planet located far beyond Neptune would likely belong ...