At a frigid -125 degrees Fahrenheit (-87 degrees Celsius), WD 1856+534 b is the coldest planet ever directly observed, ...

Researchers have found a candidate for the hypothetical Planet Nine, which could be an undiscovered giant planet way out in our solar system. However, as with all ninth planet research, the new ...

Our solar system may have a ninth planet after all, following the declassification of Pluto nearly two decades ago, ...