From atomic physics, to upper-atmospheric chemistry, to cosmology: A
  "laser photometric ratio star" to calibrate telescopes at major observatories
  The expansion of our Universe is accelerating, due to dark energy. But the
nature of dark energy has been a mystery since its discovery at the end of the
past century. In Research Highlight https://doi.org/10.1002/ntls.20220003 ,
Justin Albert, Dmitry Budker and Hossein Sadeghpour provide an overview of how
a laser photometric ratio star (a novel light source generated by laser
excitation of the Earth's upper-atmospheric sodium layer, which will radiate
equally brightly at wavelengths of 589 nm and 820 nm) can help us precisely
calibrate telescopes in order to understand the nature of dark energy.
