Spectrum of a Kilonova
Five days after an August 17 gravitational wave event, the Hubble Space Telescope pointed its spectrograph at an associated bright flare called a kilonova (which is a thousand times brighter than a classical nova). The resulting spectrum of infrared light is difficult to interpret. Spectral lines can be used to identify individual chemical elements, however the material generating this glow is moving so fast that the lines are smeared out. The peak in brightness around a wavelength of 1,100 nanometers is predicted to come from a variety of radioactive elements collectively called lanthanides, which were generated by the collision of two neutron stars.