Another demonstration of the power of “observe everything, identify later”: the first detections of NHD and ND in space2 A decade ago, many astronomical The chemistry of the interstellar medium is known mostly observations were taken with the Herschel thanks to the observation of molecular emission in the form Space Observatory (ESA/NASA). Some of of photons, corresponding to the energy lost by molecules during its rotation in the gas-phase. These signals, or spectra, them were part of the “Chemical Herschel are collected by radio-telescopes operating at millimeter/ surveys of star forming regions” (CHESS) submillimeter-wavelengths and allow the identification of the chemical composition of astronomical objects. project, by Prof. Ceccarelli. These observations collected notably all the spectra toward a However, molecules can be identified in space only if they had source called IRAS 16293 over a wide range been previously studied (and interpreted) in the laboratory. For this reason, a team of scientists from three different country of frequencies. After analyzing them for combined their facilities to study the spectrum of two radicals, the original science, the data went into the NHD and ND. These two species are isotopic forms of amidogen2 archive. radical (NH) which is an intermediate in the formation mechanism2 of interstellar ammonia (NH).3 A decade later, new spectra of NHD and While the laboratory spectrum of NH has already been studied2 ND have been measured in the laboratory; and the amidogen radical was known to exist in the interstellar 2 medium, the information available for NHD and ND were2 looking back at the old observations it was rather scarce. The spectral recording started in Bologna and possible to identify these molecules in space continued in Garching, but the narrow frequency coverage of for the first time. These results give a further the instruments did not allow a thorough interpretation of the observed features. Indeed, the spectra of such small molecules important insight into how deuterium are spread across a wide range of frequencies. chemistry operates in the interstellar medium and influences molecular evolution in star- This issue could be overcome with the use of the bright far- infrared radiation extracted by the AILES beamline at SOLEIL. and planet-forming regions. The powerful radiation source was used into a Fourier-transform interferometer to investigate the rotational spectrum of NHD and ND at higher frequency; the obtained data were then combined2 with those from the other laboratories into a joint-analysis. As a result of this work, the molecular fingerprints of NHD and ND2 could be identified for the first time in the low-mass protostar IRAS 16293 (see Figure), one of the astronomical objects observed by the Herschel telescope during its lifetime. 58