Submillimetre observations of low-mass cloud cores: forming tiny objects in situ

The origin of very low-mass objects such as brown dwarfs and 'isolated planets' is unclear: can they form in-situ from very low-mass cloud cores in a scaled-down version of star formation? Here I discuss methods of detecting and characterising such faint cores using submillimetre-wavelength observations. Some data are presented for the Ophiuchus clouds that strongly suggest there is little division between stars and ultra low-mass objects at the earliest evolutionary stages. Some challenging results have emerged (in the context of current theory), including finding cores of only a few Jupiter masses and a core mass function still rising at the mass detection limit: the implications are briefly discussed.