Suggestions that the hypothesized Planet 9 formed outside our solar system, or was even stolen from a rival solar system, have been dealt a blow by investigations into the likelihood of planetary capture by young stars. Hypothetical Planet 9. Image credit: R. Hurt, IPAC / Caltech. The presence of a new planet on the outskirts of our solar system was famously proposed by Brown and Batygin in 2016 to explain unusual clustering in the Kuiper belt, a...
