Why Supermassive Black Holes Turn Down Feasts

Supermassive black holes have a reputation for devouring everything in sight, but new observations from the Atacama Large Millimetre/submillimetre Array reveal they can be surprisingly picky eaters. Even when galaxy mergers deliver enormous amounts of cold molecular gas directly to a black hole’s doorstep, many choose to nibble rather than gorge raising questions about what triggers feeding episodes. The discovery suggests black hole growth during galaxy collisions may be far more inefficient and episodic than we previously thought.