Quasars powered by supermassive black holes have been unexpectedly vanishing. Scientists have started to figure out why.
Rosaly Lopes has visited dozens of active volcanoes on Earth and discovered even more elsewhere in the solar system. Her work is helping to establish whether volcanoes on distant moons could create conditions friendly to life.
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.