  Using the inverse scattering method we construct an exact stationary
asymptotically flat 4+1-dimensional vacuum solution describing Black Saturn: a
spherical black hole surrounded by a black ring. Angular momentum keeps the
configuration in equilibrium. Black saturn reveals a number of interesting
gravitational phenomena: (1) The balanced solution exhibits 2-fold continuous
non-uniqueness for fixed mass and angular momentum; (2) Remarkably, the 4+1d
Schwarzschild black hole is not unique, since the black ring and black hole of
black saturn can counter-rotate to give zero total angular momentum at
infinity, while maintaining balance; (3) The system cleanly demonstrates
rotational frame-dragging when a black hole with vanishing Komar angular
momentum is rotating as the black ring drags the surrounding spacetime.
Possible generalizations include multiple rings of saturn as well as doubly
spinning black saturn configurations.
