spectral energy distribution
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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 astronomical sources. For example, in
radio astronomy Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation comin ...
they are used to show the emission from synchrotron radiation, free-free emission and other emission mechanisms. In
infrared astronomy Infrared astronomy is a sub-discipline of astronomy which specializes in the observation and analysis of astronomical objects using infrared (IR) radiation. The wavelength of infrared light ranges from 0.75 to 300 micrometers, and falls in betw ...
, SEDs can be used to classify
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.


Detector for spectral energy distribution

The count rates observed from a given astronomical radiation source have no simple relationship to the flux from that source, such as might be incident at the top of the
Earth's atmosphere The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing fo ...
. This lack of a simple relationship is due in no small part to the complex properties of radiation detectors. These detector properties can be divided into *those that merely attenuate the beam, including *#residual atmosphere between source and detector, *#absorption in the detector window when present, *#quantum efficiency of the detecting medium, *those that redistribute the beam in detected energy, such as *#fluorescent photon escape phenomena, *#inherent energy resolution of the detector.


See also

*
Astronomical radio source An astronomical radio source is an object in outer space that emits strong radio waves. Radio emission comes from a wide variety of sources. Such objects are among the most extreme and energetic physical processes in the universe. History In 1932, ...
* Astronomical X-ray sources *
Background radiation Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources. Background radiation originates from a variety of source ...
*
Bremsstrahlung ''Bremsstrahlung'' (), from "to brake" and "radiation"; i.e., "braking radiation" or "deceleration radiation", is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typicall ...
*
Cosmic microwave background spectral distortions CMB spectral distortions are tiny departures of the average cosmic microwave background (CMB) frequency spectrum from the predictions given by a perfect black body. They can be produced by a number of standard and non-standard processes occurring ...
*
Cyclotron radiation Cyclotron radiation is electromagnetic radiation emitted by non-relativistic accelerating charged particles deflected by a magnetic field. The Lorentz force on the particles acts perpendicular to both the magnetic field lines and the particles' mot ...
*
Electromagnetic radiation In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) li ...
* Synchrotron radiation *
Wavelength dispersive X-ray spectroscopy Wavelength-dispersive X-ray spectroscopy (WDXS or WDS) is a non-destructive analysis technique used to obtain elemental information about a range of materials by measuring characteristic x-rays within a small wavelength range. The technique gener ...


References


Further reading

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External links


The High Energy Astrophysics Science Archive Research Center (HEASARC) at NASAThe Science of Spectroscopy
Applied and interdisciplinary physics Observational astronomy Optical phenomena Radiation Scattering Spectroscopy {{spectroscopy-stub