Kuiper Belt objects like the one New Horizons just flew past are a dime a dozen, but scientists have detailed spacecraft observations of just three such distant, frozen worlds.
Learn more about NASA's New Horizons mission, which performed history's first flyby of the Pluto system on July 14, 2015.
The most distant celestial object ever explored may well have moons, and astronomers are trying hard to find them.
The newest snowman-like image of Ultima Thule (2014 MU69), a pristine object from the dawn of the solar system, is already revealing insights into how planets form.
Names matter, even when they're temporary nicknames for objects 4.1 billion miles (6.6 billion kilometers) away from Earth.
Only moments before New Horizons flew by the most distant solar system object ever visited, astrophysicist and Queen guitarist Brian May released his new single based on the mission.
Ultima Thule, the weird Kuiper Belt object that NASA's New Horizons spacecraft visited in a historic flyby on Jan. 1, 2019, looks like a cosmic bowling pin, scientists say.
On Jan. 1, 2019, NASA's New Horizons spacecraft will make history with the first close flyby of a Kuiper Belt object: Ultima Thule. See photos of Ultima Thule and the historic encounter here!
As 2018 draws to a close, one group of people plans to celebrate something far more unusual — a flyby of Ultima Thule, the most distant solar system object ever explored. Here's what to expect.
As NASA's New Horizons probe nears its second target, we investigate what's lurking at the edge of the solar system.
NASA's New Horizons spacecraft is about the make the most distant planetary flyby in the history of spaceflight, and you can follow the action live.
At 12:33 a.m. EST on Jan. 1, 2019, a robotic emissary of humankind will fly past a never-seen-before world in the outer solar system. Here's how to watch with mobile apps.
New Horizons principal investigator Alan Stern discusses the mission and its Jan. 1 flyby of the mysterious, distant object Ultima Thule.