Spectral Energy Distribution
Encyclopedia
A spectral energy distribution (SED) is a plot of brightness or flux density versus frequency or wavelength of light. It is used in many branches of astronomy to characterize astronomical sources. For example, in radio astronomy
, an SED with a negative spectral index
around −0.7 would indicate a synchrotron radiation
source. In infrared astronomy
, SEDs can be used to classify T Tauri stars.
These detector properties can be divided into:
those that merely attenuate the beam, including—
those that redistribute the beam in detected energy such as—
Radio astronomy
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The initial detection of radio waves from an astronomical object was made in the 1930s, when Karl Jansky observed radiation coming from the Milky Way. Subsequent observations have identified a number of...
, an SED with a negative spectral index
Spectral index
In astronomy, the spectral index of a source is a measure of the dependence of radiative flux density on frequency. Given frequency \nu and radiative flux S, the spectral index \alpha is given implicitly byS\propto\nu^\alpha....
around −0.7 would indicate a synchrotron radiation
Synchrotron radiation
The electromagnetic radiation emitted when charged particles are accelerated radially is called synchrotron radiation. It is produced in synchrotrons using bending magnets, undulators and/or wigglers...
source. In infrared astronomy
Infrared astronomy
Infrared astronomy is the branch of astronomy and astrophysics that studies astronomical objects visible in infrared radiation. The wavelength of infrared light ranges from 0.75 to 300 micrometers...
, SEDs can be used to classify T Tauri stars.
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. 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, and
- quantum efficiency of the detecting medium, and
those that redistribute the beam in detected energy such as—
- fluorescent photon escape phenomena,
- inherent energy resolution of the detector.
See also
- Astronomical cosmic-ray source
- Astronomical gamma-ray source
- Astronomical infrared source
- Astronomical neutron source
- Astronomical radio source
- Astronomical ultraviolet source
- Astronomical X-ray sources
- Background radiationBackground radiationBackground radiation is the ionizing radiation constantly present in the natural environment of the Earth, which is emitted by natural and artificial sources.-Overview:Both Natural and human-made background radiation varies by location....
- BremsstrahlungBremsstrahlungBremsstrahlung is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typically an electron by an atomic nucleus. The moving particle loses kinetic energy, which is converted into a photon because energy is conserved. The term is...
- Cyclotron radiationCyclotron radiationCyclotron radiation is electromagnetic radiation emitted by moving charged particles deflected by a magnetic field. The Lorentz force on the particles acts perpendicular to both the magnetic field lines and the particles' motion through them, creating an acceleration of charged particles that...
- Electromagnetic radiationElectromagnetic radiationElectromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
- Synchrotron radiationSynchrotron radiationThe electromagnetic radiation emitted when charged particles are accelerated radially is called synchrotron radiation. It is produced in synchrotrons using bending magnets, undulators and/or wigglers...
- Wavelength dispersive X-ray spectroscopyWavelength dispersive X-ray spectroscopyThe Wavelength dispersive X-ray spectroscopy is a method used to count the number of X-rays of a specific wavelength diffracted by a crystal. The wavelength of the impinging x-ray and the crystal's lattice spacings are related by Bragg's law and produce constructive interference if they fit the...