An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

   Homepage   
   


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Number of Results: 1 Search : Hoyle state
Hoyle state
  حالت ِ هویل   
hâlat-e Hoyle

Fr.: état de Hoyle   

An → excited state in the → triple alpha process leading to the production of the most abundant → isotope of → carbon. The existence of this state is of extreme astrophysical importance concerning the → nucleosynthesis of 12C in stellar → cores:
4He + 4He ↔ 8Be,
8Be + 4He ↔ 12C*,
12C*12C + γ.
The process proceeds as follows. First the unstable → ground state of 8Be is formed in the collision of two → alpha particles. Since 8Be exists roughly 7 x 10-17 sec, it must fuse with an alpha particle before breaking up. However, the probability of three bodies merging simultaneously is extremely low. Hoyle showed that the 12C nucleus needs an excited state or resonance at 7.68 MeV to provide for a high reaction probability. The Hoyle state was soon found at 7.65 MeV with the predicted → spin and → parity.

In honor of the British astrophysicist Fred Hoyle (1915-2001), who predicted this state in 1953 (Hoyle et al. 1953, Physical Review 92, 1095); it was discovered by W. A. Fowler in 1957; → state.