  We investigate the intrinsic shapes of starless cores in the Orion GMC, using
the prestellar core sample of Nutter and Ward-Thompson (2007), which is based
on submillimeter SCUBA data. We employ a maximum-likelihood method to
reconstruct the intrinsic distribution of ellipsoid axial ratios from the axial
ratios of projected plane-of-the-sky core ellipses. We find that, independently
of the details of the assumed functional form of the distribution, there is a
strong preference for oblate cores of finite thickness. Cores with varying
finite degrees of triaxiality are a better fit than purely axisymmetric cores
although cores close to axisymmetry are not excluded by the data. The incidence
of prolate starless cores in Orion is found to be very infrequent. We also test
the consistency of the observed data with a uniform distribution of intrinsic
shapes, which is similar to those found in gravoturbulent fragmentation
simulations. This distribution is excluded at the 0.1% level. These findings
have important implications for theories of core formation within molecular
clouds.
