Luminous infrared galaxy

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Luminous infrared galaxies or LIRGs are galaxies with luminosities, the measurement of brightness, above 10¹¹ L_☉. They are also referred to as submillimeter galaxies (SMGs) through their normal method of detection. LIRGs are more abundant than starburst galaxies, Seyfert galaxies and quasi-stellar objects at comparable luminosity.^{[citation needed]} Infrared galaxies emit more energy in the infrared than at all other wavelengths combined.^[1] A LIRG's luminosity is 100 billion times that of the Sun.

Galaxies with luminosities above 10¹² L_☉ are ultraluminous infrared galaxies (ULIRGs). Galaxies exceeding 10¹³ L_☉ are characterised as hyper-luminous infrared galaxies (HyLIRGs). Those exceeding 10¹⁴ L_☉ are extremely luminous infrared galaxies (ELIRGs). Many of the LIRGs and ULIRGs are showing interactions and disruptions. Many of these types of galaxies spawn about 100 new stars a year as compared to the Milky Way which spawns one a year; this helps create the high level of luminosity.