Left panel: illustration of the nitrogen isotope heterogeneity of the solar system, adapted from Meibom et al. (2007); Mumma & Charnley (2011). Comets, meteorites, and interstellar dust particles (IDPs) are located over a range of distances from the Sun and the plotted d_Sun values should be regarded as an average value only. Right panel: ¹⁴N/¹⁵N ratios obtained from APEX measurements (black, this work) and ASTE (gray, Watanabe et al. 2012). Diamonds and triangles indicate values from HCN and HNC isotopologues, respectively. Error bars are 1σ for combined uncertainties on the calibration and the intensity. The gray bars (“cores”) indicate the prestellar core values from HCN by Hily-Blant et al. (2013a).