Comparison of nitrogen isotopic ratios obtained from comets (left) and molecular cloud core (right). The blue line indicates the ratio of nitrogen isotopes in  Earth's atmosphere while the wider yellow line indicates that of the protosolar nebula. The figure shows that the nitrogen isotopic ratios obtained from cometary molecules are similar to each other while those of HCN (hydrogen cyanide) and HN₃ (ammonia) in the molecular cloud core are different.