A nitrogen accent in the quasar's chemical orchestra
In the vast choir of galactic nuclei, some voices ring out louder than the rest. In quasars whose spectral nitrogen lines are anomalously strong, the chemical makeup of the gas in the broad-line region (the gas whipping around the black hole at enormous speeds) long remained a puzzle. Astronomers argued: is all the gas there simply rich in metals, or has nitrogen in particular been added beyond measure?