In 1965, twelve years after the first maser was built in a laboratory, a hydroxyl (OH) maser was discovered in the plane of the Milky Way. Masers of other molecules were discovered in the Milky Way in the following years, including water (H2O), silicon monoxide (SiO), and methanol (CH3OH). The typical isotropic luminosity for these galactic masers is . The first evidence for extragalactic masing was detection of the hydroxyl molecule in NGC 253 in 1973, and was roughly ten times more luminous than galactic masers.