  Crater II is an unusual object among the dwarf satellite galaxies of the
Local Group in that it has a very large size for its small luminosity. This
provides a strong test of MOND, as Crater II should be in the deep MOND regime
($g_{in} \approx 34\;\mathrm{km}^2\,\mathrm{s}^{-2}\,\mathrm{kpc}^{-1} \ll a_0
= 3700\;\mathrm{km}^2\,\mathrm{s}^{-2}\,\mathrm{kpc}^{-1}$). Despite its great
distance ($\approx 120$ kpc) from the Milky Way, the external field of the host
($g_{ex} \approx 282\; \mathrm{km}^2\,\mathrm{s}^{-2}\,\mathrm{kpc}^{-1}$)
comfortably exceeds the internal field. Consequently, Crater II should be
subject to the external field effect, a feature unique to MOND. This leads to
the prediction of a very low velocity dispersion: $\sigma_{efe} =
2.1^{+0.9}_{-0.6}\;\mathrm{km}\,\mathrm{s}^{-1}$.

Astrophysics of Galaxies