A telescope has discovered a new world on the edge of the Milky Way – potentially confirming the ‘Planet X’ theory. Beyond Neptune, a smaller ‘ninth’ planet has been identified in the Kuiper Belt. If ...

In 1906, astronomer and businessman Percival Lowell launched a search for "Planet X," a hypothetical giant planet orbiting the sun beyond Neptune. Lowell was convinced that Planet X existed based on ...

Astronomers used a telescope in Hawaii to find a new object on the outer edges of our solar system, helping to fuel evidence of a long-standing theory about Planet Nine, or Planet X. For years, ...

On a chilly morning in February 1930, a young astronomer named Clyde Tombaugh was hunched over a blinking comparator at the ...

Neptune is one of two "ice giants" in the solar system. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. Neptune is the farthest planet from the ...

It's been one Neptunian year—or about 165 Earth years—since astronomers first observed the most distant planet from the sun.

In large part, it is impossible to have escaped notice of a rather large debate swirling in the planetary community around a theorized super-Earth planet in the outer reaches of our solar system, the ...