Cometary evidence of a planet beyond Pluto — Science News, May 6, 1972
There have been suggestions that our solar system might have a tenth planet…. In the April Publications of the Astronomical Society of the Pacific, a mathematician … presents what he says is “some very interesting evidence of a planet beyond Pluto.” The evidence comes from calculations of the orbit of Halley’s comet.
Update
The 1972 evidence never yielded a planet, but astronomers haven’t stopped looking — though it became a search for Planet 9 with Pluto’s 2006 switch to dwarf status. In the mid-2010s, scientists hypothesized that the tug of a large planet 500 to 600
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