===== On the Detection of Phenalene, c-C13H10, in the ISM ===== C. Cabezas, M. Agúndez, C. Pérez, D. Villar-Castro, G. Molpeceres, D. Pérez, A. L. Steber, R. Fuentetaja, B. Tercero, N. Marcelino, A. Lesarri, P. de Vicente, and J. Cernicharo\\ reported on the\\ **[[https://doi.org/10.1051/0004-6361/202556687|Discovery of Interstellar Phenalene (c-C13H10): A new Piece in the Chemical Puzzle of PAHs in Space]]**\\ //Astron. Astrophys.// **701**, Art. No. L8 (2025).\\ Phenalene was identified through several //a//-type rotational transitions, often series easier to detect because of oblate pairing of the transitions having the same //Kc// close to //J// and then blended with weaker //b//-type transitions having equivalent quantum numbres. Some isolated //b//-type transitions were also assigned in the astronomical spectrum. The identifications were based on the QUIJOTE molecular line survey carried out with the Yebes 40 m radio telescope between 31.0 and 50.4 GHz, but phenalene assignments were made only up to 39.8 GHz. A rotational temperature of 8 K was derived. The column density of phenalene appears to be slightly larger than that of the lighter indene, albeit with considerable uncertainty.\\ \\ G. Wenzel, T. H. Speak, C. Xue, E. A. Bergin, A. M. Burkhardt, M. A. Cordiner, M. Duffy, Z. T. P. Fried, A. Lipnicky, C. N. Shingledecker, R. H. J. Willis, A. J. Remijan, M. C. McCarthy, B. A. McGuire, and I. R. Cooke\\ reported on the\\ **[[https://doi.org/10.3847/2041-8213/ae8757|Detection of the Polycyclic Aromatic Hydrocarbon Phenalene (C13H10) in the Very Low-luminosity Object MC27/L1521F]]**\\ //Astrophys. J. Lett.// **1006**, Art. No. L38 (2026).\\ The molecule was identified by line stacking of observations carried out with thw GBT 100 m dish. While the column density of phenalene is similar to the one in TMC-1 CP, but the phenalene/benzonitrile ratios differ. It is ~9 in TMC-1 CP, whereas it is ~40 in MC27/L1521F.\\ \\ ---- Contributor(s): H. S. P. Müller; 09, 2025; 08, 2026. ----