Software flagged 13 candidate pairs of infrared sources. After a manual check, only one survived. It had shifted 47.5 arcminutes across the sky in 23 years, about one and a half times the width of the full moon, and it matches what a Neptune-sized planet in the far solar system would look like.

That makes it a possible first observational hint of Planet Nine. Terry Long Phan of National Tsing Hua University in Taiwan found it during his PhD, working with colleagues in........

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