enow.com Web Search

Search results

  1. Results from the WOW.Com Content Network
  2. Half flux diameter - Wikipedia

    en.wikipedia.org/wiki/Half_flux_diameter

    The half flux diameter or HFD is a definition used by astronomers to define the star size in an astronomical image. Mainly due to the seeing, stars are not imaged as a dot but spread out like a Gaussian shape. [1] The half flux diameter defines the diameter of a circle around the bright center in which half of the star flux or energy is contained.

  3. AB magnitude - Wikipedia

    en.wikipedia.org/wiki/AB_magnitude

    The monochromatic AB magnitude is defined as the logarithm of a spectral flux density with the usual scaling of astronomical magnitudes and a zero-point of about 3 631 janskys (symbol Jy), [1] where 1 Jy = 10 −26 W Hz −1 m −2 = 10 −23 erg s −1 Hz −1 cm −2 ("about" because the true definition of the zero point is based on magnitudes as shown below).

  4. Spectral flux density - Wikipedia

    en.wikipedia.org/wiki/Spectral_flux_density

    Then the horizontal components of flux are considered to cancel each other by symmetry, leaving only the vertical component of the flux as non-zero. In this case [4] some astrophysicists think in terms of the astrophysical flux (density), which they define as the vertical component of the flux (of the above general definition) divided by the ...

  5. Spectral index - Wikipedia

    en.wikipedia.org/wiki/Spectral_index

    In astronomy, the spectral index of a source is a measure of the dependence of radiative flux density (that is, radiative flux per unit of frequency) on frequency. Given frequency ν {\displaystyle \nu } in Hz and radiative flux density S ν {\displaystyle S_{\nu }} in Jy, the spectral index α {\displaystyle \alpha } is given implicitly by S ...

  6. Flux - Wikipedia

    en.wikipedia.org/wiki/Flux

    Bottom: Field line through a curved surface, showing the setup of the unit normal and surface element to calculate flux. To calculate the flux of a vector field F (red arrows) through a surface S the surface is divided into small patches dS. The flux through each patch is equal to the normal (perpendicular) component of the field, the dot ...

  7. Photometry (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Photometry_(astronomy)

    After determining the flux of an object in counts, the flux is normally converted into instrumental magnitude. Then, the measurement is calibrated in some way. Which calibrations are used will depend in part on what type of photometry is being done. Typically, observations are processed for relative or differential photometry. [32]

  8. Jansky - Wikipedia

    en.wikipedia.org/wiki/Jansky

    The flux to which the jansky refers can be in any form of radiant energy. It was created for and is still most frequently used in reference to electromagnetic energy, especially in the context of radio astronomy. The brightest astronomical radio sources have flux densities of the order of 1–100

  9. Zero point (photometry) - Wikipedia

    en.wikipedia.org/wiki/Zero_Point_(photometry)

    In astronomy, the zero point in a photometric system is defined as the magnitude of an object that produces 1 count per second on the detector. [1] The zero point is used to calibrate a system to the standard magnitude system, as the flux detected from stars will vary from detector to detector. [2]