We propose to carry out ISOPHOT observations of a number of starless
 molecular cloud cores, which we have recently studied in a long-term
 JCMT observing programme. We discovered submillimetre continuum
 emission from Myers starless cores for the first time. We now wish to
 observe these objects in the far-ir to obtain a complete picture
 of the spectral energy distributions (SEDs), and hence temperatures,
 luminosities, masses and natures of these cores which were not
 detected by IRAS. The peaks of the SEDs will tell us the temperatures
 of these cores, which may be the coldest star formation entities ever
 studied. Our sources are ideally suited to study by ISOPHOT, since
 they are isolated regions, and have FWHM typically of 50" (see Fig.1).
 On the basis of our submillimetre observations we hypothesised that
 these cores are pre-protostellar in nature, and at an earlier
 evolutionary stage than the Class 0 protostar stage. We wish to
 obtain ISO data to test our hypothesis, and furthermore ISO presents
 a unique opportunity to test the specific predictions of models of
 ambipolar diffusion in low-mass star-forming regions such as these.

 The ISOPHOT observations will allow us to obtain luminosities for
 the sources, and thus to ascertain whether the cores are being
 internally heated by low luminosity protostars, or whether our
 hypothesis that the heating can be explained by the interstellar
 radiation field and cosmic rays is correct. In addition, when the
 ISOPHOT observations are combined with our existing submillimetre
 observations and our planned bolometer array observations, we will
 be able to test the detailed predictions of the different models
 of star formation and determine which, if any, is correct. For
 instance, our initial study has already shown that the power-law
 radial density profile of the standard model is incorrect. ISO
 should allow us to say a great deal more about these cores.