Al-26

Aluminum-26 (Al-26) is a radioactive isotope of aluminum with a half-life of approximately 717,000 years. It decays by beta-plus decay (positron emission) and electron capture to magnesium-26 (Mg-26), emitting gamma radiation at 1.809 MeV. Al-26 is notable for its long half-life and its role in astrophysical processes. It is produced through cosmic ray interactions with argon in the Earth's atmosphere and is also synthesized in supernovae and stellar nucleosynthesis.

Al-26 is primarily used in cosmochemistry and astrophysics. It serves as an important tracer for studying the early solar system and the formation of planetary bodies, as its decay influences the thermal history of meteorites. The detection of Al-26 gamma emissions in interstellar space helps astronomers study ongoing nucleosynthesis in stars and the distribution of radioactive material in the galaxy. Additionally, Al-26 is used in geochronology for dating meteorites and ancient terrestrial materials, providing insights into planetary evolution.

Al-26 is not found in significant quantities on Earth due to its long half-life and continuous decay over geological timescales. However, it is produced in the upper atmosphere through cosmic ray spallation of argon and can be found in trace amounts in meteorites, where it serves as a key isotope in understanding the history of the solar system. In space, Al-26 is generated in supernovae, massive stars, and cosmic ray interactions, and its characteristic 1.809 MeV gamma emission has been detected in the Milky Way, providing evidence of ongoing stellar nucleosynthesis.