The boundary of a solar system is not defined by planets, but by gravity. Beyond Pluto and the Kuiper Belt lies the Oort Cloud, extending up to a light year from the Sun and still considered part of ...

The Voyager spacecraft has made a groundbreaking discovery at the edge of our solar system—an astonishing 50,000-degree wall ...

CAPE CANAVERAL, Fla. (AP) - Astronomers may have found the first moon outside our solar system, a gas behemoth the size of Neptune. Plenty of planets exist beyond our solar system, but a moon around ...

Astronomers have detected the chemical fingerprint of a frozen, water-rich planetary fragment being devoured by a white dwarf star, offering the clearest evidence yet that icy, life-delivering objects ...

Add Yahoo as a preferred source to see more of our stories on Google. An illustration showing Planet Nine, a hypothetical, undiscovered planet in our solar system. New research now suggests the ...

Our Sun’s outer atmosphere, the corona, is millions of degrees hotter than it should be, and no one knows why.