We analyzed by optical spectroscopy the plume surrounding drops of yttrium oxide Y2O3 melted at the focus of a 2 kW parabolic solar furnace. The band spectra of YO molecule have been observed. These spectra result from a fluorescence phenomena excited by solar radiation. Their profiles evolution with the distance above the liquid sample reflects a dependence with the temperature. These spectra result from the emission of non-thermal equilibrium species, with vibrational temperatures from 2600 K down to 600 K. From our knowledge such low temperature YO spectra are reported for the first time. (C) 2002 Elsevier Science B.V. All rights reserved.