Far beyond Neptune, something heavy appears to be tugging on the outer solar system, bending the paths of distant icy worlds in ways gravity alone should be able to explain. Planet 9, still invisible ...

Earth has a newly-discovered neighbor in the solar system. But the heavenly body – possibly a dwarf planet à la Pluto – isn't a frequent visitor. Located beyond Neptune, its extreme orbit ...

Scientists examined infrared space surveys to narrow down candidates for Planet 9. Planet 9 would be so far from the Sun that it is just not illuminated by much sunlight. The two space surveys, ...

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