Our solar system now, once again, officially consists of only eight planets. Although largely debunked, speculation continued ...

When you buy through links on our articles, Future and its syndication partners may earn a commission. Astronomers have been actively hunting for a ninth planet in the solar system for almost a decade ...

The search for an unknown planet in our solar system has inspired astronomers for more than a century. Now, a recent study suggests a potential new candidate, which the paper’s authors have dubbed ...

Planet Y is the latest in a series of hypothetical solar system planets that scientists have proposed in recent years, all with slightly different characteristics, but collectively believed to be ...

But the hunt restarted in 2016, when Caltech astronomers Mike Brown and Konstantin Batygin proposed their Planet Nine hypothesis ... as Planet X, likely lurks somewhere within the Kuiper Belt — a ...

Exoplanet hunters Christopher Watson and Annelies Mortier explain the long search for a 'twin Earth' capable of sustaining ...