PLANET NINE CONTROVERSY THE SOLAR SYSTEM'S BLACK HOLE

It’s been four years since Mike Brown, the astronomer who removed Pluto’s status as a planet, added a hypothetical one back in to explain strange orbits in the outer Solar System. In another two years the Vera C. Rubin Observatory will map those celestial backwaters to help find Brown’s Planet Nine. But what if this target can’t be seen? It’s a possibility that hit the headlines last year when Planet Nine was replaced, at least in excited media headlines, by an ancient black hole. Brown himself addressed the possibility, writing on Twitter: “P9 could definitely be a black hole, as long as it is the right mass. In fact, it could also be a six-Earth-mass hamburger.” So is a black hole lurking in the outer Solar System a statistical possibility worth considering? Or a whopper of a stab in the dark?

Answers are out there among trans-Neptunian objects (TNOs). Ancient debris left over from planet formation, the TNOs were swept up by a young, migrating Neptune and dumped far from the Sun in the Kuiper Belt. The ice giant’s hold on this ring of rubble continues today, though its influence has changed. Once the source of gravitational chaos,