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(WHTM) – Our solar system has eight (was nine) planets and is roughly 4.571 billion years old. The planets in our solar system include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune ...

Astronomers from Princeton and other institutions have discovered the smallest planet found outside of our solar system using a technique that researchers believe will uncover others that potentially ...

SEATTLE – NASA has discovered the smallest planet ever seen beyond our solar system – a rocky world just 1.4 times larger than Earth – using its planet-hunting Kepler observatory. The planet, called ...

A spacecraft operated by the European Space Agency and the Japan Aerospace Exploration Agency has made its final flyby of Mercury, as scientists now work to guide BepiColombo into the planet’s orbit.

If confirmed, the planetary system around HD 10180, a star more than 100 light years distant, would be the richest-ever discovered. One astronomer says it's part of a growing body of evidence that the ...

A large asteroid could be reclassified as a dwarf planet -- which could make it the smallest in the solar system -- after new research revealed it's shape, astronomers said on Monday. A large asteroid ...

Astronomers have detected the smallest rogue planet in our Milky Way galaxy, and it's between the sizes of Mars and Earth. Rogue planets are free-floating planets that don't orbit stars. Astronomers ...

Mercury is the innermost and smallest of the eight major planets in our Solar System, orbiting closest to the Sun. Though ...

(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 ...