In August, an amateur French astronomer, Adrien Coffinet, messaged an email list dedicated to asteroid and comet research with an announcement. He’d identified a new quasi-moon: “2025 PN7 seems to be a quasi-satellite of the Earth,” he wrote. Last week, news of the quasi-moon went mainstream, as a surge of headlines declared that Earth officially had a second moon. This isn’t exactly right: As several scientists reiterated to me, Earth still only has one real moon. But as researchers have