A black hole at the centre of a quasar at a redshift of z = 4 is accreting the mass of the Sun every day. The quasar’s extreme luminosity is equivalent to 50,000 times that of the Milky Way. Its broad-line region should be resolvable observationally and will provide an important test for broad-line region size–luminosity relationships.
- Christian Wolf
- Samuel Lai
- Rachel L. Webster