The Quasar SDSS J140821.67+025733.2 Does Not Contain a 196 Billion Solar Mass Black Hole

The black hole in the quasar SDSS J140821.67+025733.2 has been reported to have a mass of 1.96 × 1011 M⊙ based on measurements from the SDSS DR12 Quasar Catalog. As a result, references to this object as the most massive known black hole in the universe have recently appeared in scientific articles and in popular media including Wikipedia. We show that this extremely high mass estimate is incorrect, resulting from a faulty measurement of the C iv line width. From a new measurement of the Mg ii line width, we derive an estimate of MBH ≈ 8 × 109 M⊙.