Some explosions in space last only a few days, but at their peak they outshine entire galaxies. These are LFBOTs — rapid blue transients. They are rare and have been a mystery until now.
Astronomers studied 11 such events. Analysis of brightness and light composition revealed that they all occur in dwarf galaxies with intense star formation. The oddity is that the flashes avoid bright stellar nurseries and appear on desolate outskirts.
The best model: a merger of a dead star the size of a city and a massive dying giant. This is not a supernova from core collapse, but a cosmic accident. Back in the 1930s, Fritz Zwicky suggested that some cataclysms give birth to neutron stars. Today, his insight helps us understand the nature of these fleeting blue ghosts.
Astronomers call 'metallicity' the fraction of heavy elements in stellar gas. The lower the metallicity, the more 'virgin' the material. LFBOTs prefer 'moderate dirt' — not pristine gas, but not heavily enriched with heavy elements either.