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.

Astronomers at UCL and the University of Warwick, as part of a global collaboration including partners in Chile, USA and ...

OF201 is incredibly lightweight on a cosmic scale. Scientists estimate its mass is about 20,000 times less than Earth’s and ...

A recently discovered celestial body is rewriting our knowledge of the Kuiper Belt and maybe challenging the existence of the ...

The International Astronomical Union’s Minor Planet Center, which catalogs new moons and other small bodies in the solar ...

In a thrilling development that challenges long-held assumptions about the outer reaches of our solar system, astronomers ...

A recent study found that Jupiter was once twice the size that it is now, making it big enough to swallow up 2,000 Earths.

Some became rocks the size of baseballs, others the size of a house, and a few as big as a planet. This process, called accretion, is how everything in the solar system – planets, moons, comets and ...

The presence of water-ice in the debris disk around a young star could have helped facilitate the growth and development of ...

Pluto was reclassified as a dwarf planet in 2006. Our solar system may have a ninth planet ... scientists say The hidden candidate is likely the size of Neptune and is so far away that it could ...

An international team used 40 years' worth of data from two space probes to track down what they believe are signs of this distant planet moving around our sun.

Without a firm lower limit on size or mass, we’re forced to say the solar system has hundreds of planets—maybe thousands ... but when you compare any two samples close together on that ...