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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).
The conversion factor is 10 8 maxwell per weber, since flux is the integral of field over an area, area having the units of the square of distance, thus 10 4 G/T (magnetic field conversion factor) times the square of 10 2 cm/m (linear distance conversion factor). 10 8 Mx/Wb = 10 4 G/T × (10 2 cm/m) 2.
If the magnetic field is constant, the magnetic flux passing through a surface of vector area S is = = , where B is the magnitude of the magnetic field (the magnetic flux density) having the unit of Wb/m 2 , S is the area of the surface, and θ is the angle between the magnetic field lines and the normal (perpendicular) to S.
The flux density of astronomical sources is many orders of magnitude below 1 W·m −2 ·Hz −1, so the result is multiplied by 10 26 to get a more appropriate unit for natural astrophysical phenomena. [7] The millijansky, mJy, was sometimes referred to as a milli-flux unit (mfu) in older astronomical literature. [8]
For objects within the immediate neighborhood of the Sun, the absolute magnitude M and apparent magnitude m from any distance d (in parsecs, with 1 pc = 3.2616 light-years) are related by = = (), where F is the radiant flux measured at distance d (in parsecs), F 10 the radiant flux measured at distance 10 pc.
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]
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phenomena, flux is a vector quantity, describing the magnitude and direction of the flow of a substance or ...
The (superconducting) magnetic flux quantum Φ 0 = h/(2e) ≈ 2.067 833 848... × 10 −15 Wb [3] is a combination of fundamental physical constants: the Planck constant h and the electron charge e. Its value is, therefore, the same for any superconductor.