<i>Colloquium</i>: Status of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>-particle condensate structure of the Hoyle state

In 1954, Fred Hoyle made a prediction regarding the existence of a resonant state of carbon-12 that would be associated with a triple-alpha process which would be fundamental in nucleosynthesis in stars and would explain the amount of carbon-12 in the Universe. This prediction was spectacularly confirmed by experiments. Nevertheless, the precise properties of the Hoyle state are still the subject of investigation. This Colloquium describes the current theoretical and experimental investigation of this important prediction.