Probing the evolving massive star population in Orion with kinematic and radioactive tracers

The interstellar medium, as seen in HI and other tracers, is marked by immense cavities or bubbles presumed to be caused by winds and supernova explosions associated with OB associations. One of the closest is the Eridanus supperbubble associated with the OB association, Orion OB1, which is studied by Voss et al. in an article highlighted in this issue. The authors quantify the energy input from the OB stars during the lifetime of the superbubble (roughly 10 Myr) and compare the expected input of radioactive species such as ²⁶Al with observed gamma ray lines emitted by the same species. The agreement with both the observed ²⁶Al 1.8 MeV intensity and the kinetic energy estimated from HI is better than a factor 2.