Today, many news outlets reported that scientists had excitedly revealed that they had reason to believe a ninth planet could once again be added to our solar system. At least, in theory.

Before you rush to sharpie “PLANET X” onto your full-wall map of our planetary neighbors, consider these words of warning from New Horizons Principal Investigator and actual scientist Alan Stern via The Associated Press: “This kind of thing comes around every few years. To date, none of those predicts have been borne out by discoveries”

Well, that’s not quite the hype of some of the headlines. In fairness, this isn’t the only “every few years” story to occasionally make the rounds of the news media with a fervour of something newly discovered, and many of the stories do contain disclaimers further down in the text. But the research behind the sadly most likely misleading headline is still fascinating.

Basically, the orbits of a lot of the planets, dwarf planets and other space debris in the outer reaches of the solar system behaves weirdly. One likely explanation for this, and perhaps even the most likely explanation, is that there’s something out there that’s creating enough of a gravity pull to disrupt its neighbors. Judging by how much the known orbits are affected, astrophysicists have come up with a theory about what a such a missing planet would look like. But nobody has ever directly seen “Planet Nine.” Not yet, anyway. And it’s even possible, although apparently less likely, that the planets are just all behaving erratically for some other reason altogether. Space is a really weird place, and the more we learn about it the weirder it seems.

Photo credit: California Institute of Technology

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