One way for black holes to form is in supernovae, or the deaths of massive stars. However, our current knowledge of stellar evolution and supernovae suggests that black holes with masses between 55 and 120 solar masses can’t be produced via supernovae. Gravitational-wave signals from black hole mergers offer us an observational test of this “gap” in black hole masses.
The supernova SN 2016iet, which might be one of the first observed pair-instability supernovae. The lines show the placement of the instrument used to take spectra of the supernova. [Adapted from Gomez et al. 2019]
Black Hole Boundaries
You need a massive star to go supernova to produce a black hole. Unfortunately, extremely massive stars explode so violently they leave nothing behind! This scenario can occur with pair-instability supernovae, which happens in stars with core masses between 40 and 135 solar masses. The “pair” in “pair-instability” refers to the electron–positron pairs that are produced by gamma rays interacting with nuclei in the star’s core. Energy is lost in this process, meaning that there’s less resistance to gravitational collapse.
As the star collapses further, two things can happen. If the star is sufficiently massive, its core ignites in an explosion that ...