NASA @NASA
A PeVatron isn't a robot from a 1950s sci-fi movie: it's a scientific term, a source for some of the highest-energy particles known to whip across our galaxy. PeVatrons are notoriously hard to pin down—but our Fermi telescope might be closing in on one: https://t.co/Y0jmfBYRyr https://t.co/BcL1n2hh4J — PolitiTweet.org