  Elucidating the appropriate microscopic degrees of freedom within neutron
stars remains an open question which impacts nuclear physics, particle physics
and astrophysics. The recent discovery of the first non-trivial dibaryon, the
$d^*(2380)$, provides a new candidate for an exotic degree of freedom in the
nuclear equation of state at high matter densities. In this paper a first
calculation of the role of the $d^*(2380)$ in neutron stars is performed, based
on a relativistic mean field description of the nucleonic degrees of freedom
supplemented by a free boson gas of $d^*(2380)$. The calculations indicate that
the $d^*(2380)$ would appear at densities around three times normal nuclear
matter saturation density, influencing the upper mass limit for a stable
neutron star and the neutron and proton fractions. New possibilities for
neutron star cooling mechanisms arising from the $d^*(2380)$ are also
predicted.
