Add Yahoo as a preferred source to see more of our stories on Google. Our solar system may have a ninth planet after all, researchers say. The possibility that an additional planet may be hidden far ...

If the solar system does have a Planet Nine, it is a world that was bullied by its larger siblings, exiled to the far reaches of space and only rescued from oblivion thanks to the intervention of ...

With the same data but a different statistical analysis, researchers have spotted two additional planets in a system that was already thought to host seven of them ...

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 ...

After studying thousands of computer simulations of the solar system, researchers at Rice University and the Planetary Science Institute think there’s a 40% chance an elusive “Planet Nine” or “Planet ...

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 ...

Twenty years after Pluto lost its planetary status, the debate continues as scientists still disagree over what defines a ...

Beginning about 4.5 billion years ago, the theory goes, a galactic cloud of interstellar gas and dust collapsed and ignited in a blaze of thermonuclear fusion to create our Sun. Swirling around that ...

Our solar system may have a ninth planet after all, researchers say. The possibility that an additional planet may be hidden far into the solar system was touted more than a century ago. But ...