Rare isotope sheds light on how dead stars re-ignite
Nuclear Astrophysics Nuclear Structure and DynamicsRare isotope sheds light on how dead stars re-ignite: Novae are stellar element-making explosions caused when a white dwarf, the carbon-cinder of a once giant star, accretes hydrogen-rich material onto its surface from a companion star. A key to help astrophysicists better understand novae is through determining the rates of reactions that create and destroy the key rare isotopes they're observed to produce, including sodium-22 (22Na). As reported in Physical Review C (2016) scientists used DSL to determine, for the first time using the Doppler-shift attenuation method, the lifetimes of several energetic states magnesium-23 (23Mg) the rare isotope that dominates the destruction of 22Na. The researchers' more precise lifetime measurements of related states help explain the structure and behaviour of these rare isotopes and thus the underlying nuclear physics driving novae.
Measurement of Lifetimes in 23Mg
O.S. Kirsebom et al., Phys. Rev. C, 9302 (2016)
How old are the oldest stars?
Nuclear AstrophysicsHow old are the oldest stars? Using DSL, scientists have helped astrophysicists narrow-in on a key cosmic mystery: the age of the oldest stars in the Milky Way. To infer a star's age from its starlight, astrophysicists need to know the rates of nuclear reactions powering it, in particular the rate of the reaction when 14N captures a proton to become 15O. It's the slowest reaction, and thus determines the overall pace, of the carbon-nitrogen-oxygen cycle of hydrogen burning in stars. As reported in Physical Review C (2014), using the DSL facility, scientists measured the 6.79 MeV energy state and others in 15O and constrained its lifetime to be less than 1.8 femtoseconds, or quadrillionths of a second. The researchers believe that even more precise reaction rates could come from coupling the DSL facility to TRIUMF's new recoil spectrometer EMMA.
Lifetime measurements of states in 15O
N. Galinski, S.K.L. Sjue et al., Phys. Rev. C, 903 (2014)