Interstellar methanol masers

Extract

The asymmetric rotor molecule methanol (CH₃OH) has hundreds of transitions at centimeter-, millimeter-, and submillimeter wavelengths. Many of these are excited in the hot (T ≳ 150 K), dense (n ≳ 10⁶ cm⁻³) molecular cloud cores surrounding newly formed massive stars or protostars. The high temperatures in these cores cause evaporation of icy grain mantles, releasing copious amounts of complex molecules, such as methanol, in the gas phase, which in hot cores has abundances (up to 10⁻⁶ relative to H₂) that are two or more orders of magnitude higher than in cold dark clouds.