While we know that intermediate-mass black holes should exist, little is known about their origins or characteristics—they are considered the rare "missing links" in black hole evolution.

Department of Inorganic and Organic Chemistry, Section of Organic Chemistry, and Institut de Biomedicina de la Universitat de Barcelona, Universitat de Barcelona, Carrer Martí i Franqués 1−11, 08028 ...

Edited by Alexis T. Bell, University of California, Berkeley, CA, and approved August 17, 2018 (received for review February 6, 2018) ...