When you buy through links on our articles, Future and its syndication partners may earn a commission. The heart-shaped Tombaugh Regio feature on the surface of Pluto. | Credit: NASA/Johns Hopkins ...

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. Labelled as planet X, prominent astronomers ...

NEW YORK (AP) — A new Tatooine-like planet outside the solar system may orbit two failed stars, scientists reported Wednesday. Located about 120 light years away, the exoplanet appears to take an ...

The International Astronomical Union defines a planet as a celestial body that orbits the sun, is massive enough that gravity has forced it into a spherical shape, and has cleared away other objects ...

(Correction: An earlier version of this story misstated how far Pluto is from the sun. The correct number is 3.7 billion miles.) What was discovered in Flagstaff, Arizona, and killed off in Prague? If ...

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Lowell Observatory's sixth annual "I Heart Pluto Festival" will honor the remote icy world that was reclassified as a dwarf planet in 2006 When you purchase through links on our site, we may earn an ...