Unexpectedly Vanishing Quasars Are Mystifying Scientists
Some quasars, powered by supermassive black holes, have been shutting down ahead of schedule. A sort of "murder-suicide pact" could explain it.
A New World’s Extraordinary Orbit Points to Planet Nine
Astronomers argue that there’s an undiscovered giant planet far beyond the orbit of Neptune. A newly discovered rocky body has added evidence to the circumstantial case for it.