The joint European-Japanese mission is only the second survey of Mercury, the least explored planet in the inner solar system. A European-Japanese spacecraft has beamed back some of the best close ...

A European-Japanese spacecraft has beamed back some of the best close-up photos yet of Mercury's north pole as part of only ...

Astronomers have discovered a rare in-sync solar system with six planets moving like a grand cosmic orchestra, untouched by outside forces since their birth billions of years ago. The find ...

Astronomers using planet-hunting satellites have discovered a rare solar system with six planets moving completely in sync with one another, as if they were untouched by any outside force since ...

All of our solar system’s planets are lining up to parade through the night sky at once. This extraordinary celestial event will see the sky scattered with seven visible planets in what is known ...

They were right. Today there are five known dwarf planets in the Solar System. The conditions for what classifies a “planet” as opposed to a “dwarf planet” were set by the International ...

Pluto was reclassified as a dwarf planet in 2006. Our solar system may have a ninth planet after all, researchers say. The possibility that an additional planet may be hidden far into the solar ...

Check out the rest of the series. If you were born in the last century you might have memorized that there were nine planets in our solar system, as heard in the famous Schoolhouse Rock!

In 2006, updated research led to Pluto being controversially demoted to dwarf planet status by the International Astronomical Union. The reasoning was that Pluto's location in the far-flung Trans ...