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A(B) and A(V) are the total extinction at the B and V filter bands. Another measure used in the literature is the absolute extinction A(λ)/A(V) at wavelength λ, comparing the total extinction at that wavelength to that at the V band. R(V) is known to be correlated with the average size of the dust grains causing the extinction.
Cosmic dust – also called extraterrestrial dust, space dust, or star dust – is dust that occurs in outer space or has fallen onto Earth. [ 1 ] [ 2 ] Most cosmic dust particles measure between a few molecules and 0.1 mm (100 μm ), such as micrometeoroids (<30 μm) and meteoroids (>30 μm). [ 3 ]
The photoelectron flux of carbon or silicate particles from the average galactic UV radiation is 1.4 × 10 10 electrons per m 2. The resultant surface potential of the dust particles is ~+0.5 V. In the hot but tenuous plasma of the Local Bubble (density 10 5 m −3, energy 100 eV) dust will be charged to +5 to +10 V surface potential. [168]
The remainder of the photon's energy gives the ejected electron kinetic energy which heats the gas through collisions with other particles. A typical size distribution of dust grains is n(r) ∝ r −3.5, where r is the radius of the dust particle. [10] Assuming this, the projected grain surface area distribution is πr 2 n(r) ∝ r −1.5 ...
For this reason, dust models are often employed in cosmology as models of a toy universe, in which the dust particles are considered as highly idealized models of galaxies, clusters, or superclusters. In astrophysics, dust models have been employed as models of gravitational collapse. Dust solutions can also be used to model finite rotating ...
The Earth's orbit is known with an absolute precision of a few meters and a relative precision of a few parts in 100 billion (1 × 10 −11). Historically, observations of Venus transits were crucial in determining the AU; in the first half of the 20th century, observations of asteroids were also important.
The Sun's passage through the higher density spiral arms of the galaxy, rather than its passage through the plane of the galaxy, could hypothetically coincide with mass extinction on Earth. [5] However, a reanalysis of the effects of the Sun's transit through the spiral structure based on CO data has failed to find a correlation.
The radiative transfer equation is a monochromatic equation to calculate radiance in a single layer of the Earth's atmosphere. To calculate the radiance for a spectral region with a finite width (e.g., to estimate the Earth's energy budget or simulate an instrument response), one has to integrate this over a band of frequencies (or wavelengths ...