An infrared excess is a measurement of an astronomical source, typically a star, that in their

spectral energy distribution A spectral energy distribution (SED) is a plot of energy versus frequency or wavelength of light (not to be confused with a 'spectrum' of flux density vs frequency or wavelength). It is used in many branches of astronomy to characterize astron ...

has a greater measured

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

flux than expected by assuming the star is a blackbody radiator. Infrared excesses are often the result of circumstellar dust heated by starlight and reemitted at longer wavelengths. They are common in

young stellar object Young stellar object (YSO) denotes a star in its early stage of evolution. This class consists of two groups of objects: protostars and pre-main-sequence stars. Classification by spectral energy distribution A star forms by accumulation of mate ...

s and evolved stars on the asymptotic giant branch or

older Older is the comparative form of "old". It may also refer to: Music: * ''Older'' (album), the third studio album from George Michael (released in 1996) ** "Older" (George Michael song) * "Older", a song on the 1999 album '' Long Tall Weekend'' ...

. In addition, monitoring for infrared excess emission from stellar systems is one possible method that could enable a search for large-scale stellar engineering projects of a hypothetical extraterrestrial civilization; for example a

Dyson sphere A Dyson sphere is a hypothetical megastructure that completely encompasses a star and captures a large percentage of its solar power output. The concept is a thought experiment that attempts to explain how a spacefaring civilization would meet ...

or Dyson swarm. This infrared excess would be the outcome of the waste heat emitted by the aforementioned structures if they are considered blackbodies at temperatures close to 300 K.

References

Observational astronomy {{astronomy-stub