The shape of a planet's orbit is one of its fundamental properties, along with its size and distance from its host star. Earth has a nearly circular orbit, but some planets outside our solar system, ...

Jupiter, the largest planet in the solar system, was 2 to 2.5 times bigger in its earlier life, according to new research. Jupiter, the largest planet orbiting the sun, used to be much bigger and ...

Studying the orbits of thousands of exoplanets shows that large planets tend to have elliptical orbits, while smaller planets tend to have more circular orbits. This split coincides with several other ...

LONDON — The search for an unknown planet in our solar system has inspired astronomers for more than a century. Now, a recent study suggests a potential new candidate, which the paper's authors have ...

A newly studied solar system breaks the usual planet pattern, raising fresh questions about how rocky and gas planets form.

Astronomers are closing in on one of the most tantalizing possibilities in planetary science, evidence that a previously unknown world may be lurking in the outer reaches of the solar system. The ...

Scientists may have discovered a dwarf planet far beyond Neptune — an unearthing that may disprove a longstanding theory about the possibility of a giant ninth planet. The dwarf planet's existence ...