For decades, our solar system was thought to have nine planets, with Pluto considered the smallest and farthest. But in 2006, Pluto was officially reclassified as a dwarf planet by the ...

Currently, our solar system recognizes 8 planets, with Pluto being demoted to a dwarf planet floating in the Kuiper Belt in 2006. Planet Nine's gravitational pull may explain what keeps the icy ...

Astronomers have spotted centimeter-sized “pebbles” swirling around two infant stars 450 light-years away, revealing the raw ...

A potential dwarf planet has been discovered in the outer reaches of our solar system, orbiting beyond Neptune. Its presence there challenges the existence of a hypothetical body known as Planet 9 ...

Artist's impression of Planet Nine – a suspected “wide-orbit” planet – with the Sun in the distance; Neptune's orbit is shown ...

Planet Nine is a hypothesized massive planet, first proposed in 2014, that is speculated to orbit far out in the solar system. It has not been detected formally.

Scientists may have discovered a dwarf planet far beyond Neptune — an unearthing that may disprove a longstanding theory ...

A fascinating glimpse into how a solar system like our own is born has been revealed with the detection of planet-forming ...

For the dwarf planet candidate, one trip around the sun takes over 24,000 years. Its orbit challenges a proposed path for a hypothetical Planet Nine.

A small, inconspicuous meteorite may be about to change our understanding of how and when our solar system formed. Tiny shavings from the meteorite Northwest Africa 12264 are challenging the long-held ...

Our solar system may have a ninth planet after all, following the declassification of Pluto nearly two decades ago, researchers say. ABC News. Video. Live. Shows. Shop. Log In. Stream on.