In 1906, astronomer and businessman Percival Lowell launched a search for "Planet X," a hypothetical giant planet orbiting the sun beyond Neptune. Lowell was convinced that Planet X existed based on some supposed irregularities he had observed in the orbits of Neptune and Uranus. His belief eventually led to the discovery of Pluto in 1930, though scientists later determined that the dwarf planet was too small to have a gravitational impact on Neptune's orbit (let alone Uranus').
Today, the Planet X hypothesis is largely considered to be discredited. However, that hasn't stopped astronomers from looking for planets in the far reaches of the solar system. And according to a new study, they might be out there — only much farther away than Lowell could have predicted.
An international team of researchers recently simulated the unstable celestial mechanics of the early solar system. They found that there is a possibility that one or more planet-size bodies came to rest in the Oort cloud, a vast collection of icy objects stretching between a few hundred billion to several trillion miles from the sun, according to NASA. The new paper describing the work has been published to the preprint server arXiv and has yet to be peer-reviewed.
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