Infrared excess
Encyclopedia
An infrared excess is a measurement of an astronomical source, typically a star
, that has a greater measured infrared
flux
than expected by assuming the star is a blackbody radiator. Infrared excesses are often the result of circumstellar dust
and are common in young stellar object
s and evolved stars on the asymptotic giant branch
or older.
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
, that has a greater measured infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
flux
Radiative flux
Radiative flux, or radiative flux density, is the amount of power radiated through a given area, in the form of photons or other elementary particles, typically measured in W/m2. It is used in astronomy to determine the magnitude and spectral class of a star...
than expected by assuming the star is a blackbody radiator. Infrared excesses are often the result of circumstellar dust
Circumstellar dust
Circumstellar Dust is astronomical dust around a star. It can be in the form of a spherical shell or a disk, e.g. an accretion disk. Circumstellar dust can be responsible for significant extinction and is usually the source of an infrared excess for stars that have it.The motion of circumstellar...
and are common in young stellar object
Young stellar object
Young stellar object denotes a star in its early stage of evolution.This class consists of two groups of objects: protostars and pre–main sequence stars. Sometimes they are divided by mass - massive YSO , intermediate mass YSO and brown dwarfs....
s and evolved stars on the asymptotic giant branch
Asymptotic Giant Branch
The asymptotic giant branch is the region of the Hertzsprung-Russell diagram populated by evolving low to medium-mass stars. This is a period of stellar evolution undertaken by all low to intermediate mass stars late in their lives....
or older.