CAPE CANAVERAL, FL -- Come Tuesday, Clyde Tombaugh will pass within 7,800 miles of the icy world he discovered 85 years ago. His ashes are flying on NASA's New Horizons spacecraft on humanity's first ...

For the first time in years, astronomers are seriously talking about adding a new member to the solar system’s planetary ...

Today, the dwarf planet Pluto orbits the sun from the edge of our solar system and its surface temperature is an inhospitable negative 378 to negative 396 degrees Fahrenheit. But a new study suggests ...

Pluto may have been demoted to non-planet status, but it still commands a court of five moons, as is fitting for the king of darkness; after all, Pluto is the Roman equivalent of the Greek God Hades.

Nearly a century after Pluto’s discovery, astronomers are still hunting for mysterious planets beyond Neptune - including a ...

Since Pluto's discovery in 1930, there have been nine planets in the solar system, but a year ago, scientists at the California Institute of Technology said there were ten. An object they called Xena ...

LONDON — 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 ...

Your 1996 column on the mysterious giant Planet X some astronomers thought might lurk beyond Pluto is in need of an update. In particular, you should tell the story of the dwarf planet Eris, whose ...

Beyond Pluto -- So others can follow -- These old walls -- Stars that move and fade -- To watch them dance -- Our star, our sun -- Seek and destroy -- Telescope wars ...