ExoMol molecular line lists XX: a comprehensive line list for H$_3^+$
  H$_3^+$ is a ubiquitous and important astronomical species whose spectrum has
been observed in the interstellar medium, planets and tentatively in the
remnants of supernova SN1897a. Its role as a cooler is important for gas giant
planets and exoplanets, and possibly the early Universe. All this makes the
spectral properties, cooling function and partition function of H$_3^+$ key
parameters for astronomical models and analysis. A new high-accuracy, very
extensive line list for H$_3^+$ called MiZATeP was computed as part of the
ExoMol project alongside a temperature-dependent cooling function and partition
function as well as lifetimes for %individual excited states. These data are
made available in electronic form as supplementary data to this article and at
http://www.exomol.com
