R136b has the spectral type of Wolf–Rayet star, with strong emission lines.[4] Although it shows enhanced helium and nitrogen at its surface, it is still a very young star, still burning hydrogen in its core via the CNO cycle, and still effectively a main sequence object.[5] Others studies classify the spectrum as a hot supergiant with emission lines of ionised nitrogen and helium, still considering it to be a young star at the core-hydrogen-burning stage, the unusual spectrum caused by strong convection and stellar winds.[2]
^ abcdDoran, E. I.; Crowther, P. A.; De Koter, A.; Evans, C. J.; McEvoy, C.; Walborn, N. R.; Bastian, N.; Bestenlehner, J. M.; Gräfener, G.; Herrero, A.; Köhler, K.; Maíz Apellániz, J.; Najarro, F.; Puls, J.; Sana, H.; Schneider, F. R. N.; Taylor, W. D.; Van Loon, J. Th.; Vink, J. S. (2013). "The VLT-FLAMES Tarantula Survey. XI. A census of the hot luminous stars and their feedback in 30 Doradus". Astronomy & Astrophysics. 558: A134. arXiv:1308.3412. Bibcode:2013A&A...558A.134D. doi:10.1051/0004-6361/201321824. S2CID118510909.