  The QCD phase diagram at densities relevant to neutron stars remains elusive,
mainly due to the fermion-sign problem. At the same time, a plethora of
possible phases has been predicted in models. Meanwhile $G_2$-QCD, for which
the $SU(3)$ gauge group of QCD is replaced by the exceptional Lie group $G_2$,
does not have a sign problem and can be simulated at such densities using
standard lattice techniques. It thus provides benchmarks to models and
functional continuum methods, and it serves to unravel the nature of possible
phases of strongly interacting matter at high densities. Instrumental in
understanding these phases is that $G_2$-QCD has fermionic baryons, and that it
can therefore sustain a baryonic Fermi surface. Because the baryon spectrum of
$G_2$-QCD also contains bosonic diquark and probably other more exotic states,
it is important to understand this spectrum before one can disentangle the
corresponding contributions to the baryon density. Here we present the first
systematic study of this spectrum from lattice simulations at different quark
masses. This allows us to relate the mass hierarchy, ranging from scalar
would-be-Goldstone bosons and intermediate vector bosons to the $G_2$-nucleons
and deltas, to individual structures observed in the total baryon density at
finite chemical potential.
