Add Yahoo as a preferred source to see more of our stories on Google. Just because Pluto was ruled out as a planet in 2006 doesn’t mean our solar system only has eight planets. The search for Planet ...

To be a planet, NASA says an object must be big enough that its gravity has cleared away any other objects of a similar size ...

The small world was found during a search for the hypothetical Planet Nine, and astronomers say the next time it will reach its closest point to the sun is in the year 26186. By Kenneth Chang Kenneth ...

Mercury will be farthest from the sun on Tuesday (Aug. 19), granting early risers a perfect opportunity to spot the fleet-footed world somewhat separated from the glare of our parent star. Mercury ...