Discovery of molecular hydrogen in SN 1987A

Both CO and SiO have been observed at early and late phases in SN 1987A. H₂ was predicted to form at roughly the same time as these molecules, but was not detected at early epochs. Here, we report the detection of NIR lines from H₂ at 2.12 and $2.40\mu m$ in VLT/SINFONI spectra obtained between days 6489 and 10,120. The emission is concentrated to the core of the SN in contrast to Hα and approximately coincides with the [Si i]/[Fe ii] emission detected previously in the ejecta. Different excitation mechanisms and power sources of the emission are discussed. From the nearly constant H₂ luminosities, we favor excitation resulting from the ${}^{44}Ti$ decay.