  Boson stars are descendants of the so-called geons of Wheeler, except that
they are built from scalar particles instead of electromagnetic fields. If
scalar fields exist in nature, such localized configurations kept together by
their self-generated gravitational field can form within Einstein's general
relativity. In the case of complex scalar fields, an absolutely stable branch
of such non-topological solitons with conserved particle number exists. Our
present surge stems from the speculative possibility that these compact objects
could provide a considerable fraction of the non-baryonic part of dark matter.
In any case, they may serve as a convenient "laboratory" for studying
numerically rapidly rotating bodies in general relativity and the generation of
gravitational waves.
