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Optical depth in astrophysics refers to a specific level of transparency. Optical depth and actual depth, τ {\displaystyle \tau } and z {\displaystyle z} respectively, can vary widely depending on the absorptivity of the astrophysical environment.
Spectral optical depth or spectral optical thickness is the natural logarithm of the ratio of incident to transmitted spectral radiant power through a material. [1] Optical depth is dimensionless , and in particular is not a length, though it is a monotonically increasing function of optical path length , and approaches zero as the path length ...
The early writers discussed here treated vision more as a geometrical than as a physical, physiological, or psychological problem. The first known author of a treatise on geometrical optics was the geometer Euclid (c. 325 BC–265 BC).
The "Big Bang" scenario, with cosmic inflation and standard particle physics, is the only cosmological model consistent with the observed continuing expansion of space, the observed distribution of lighter elements in the universe (hydrogen, helium, and lithium), and the spatial texture of minute irregularities (anisotropies) in the CMB radiation.
The density, mass, and location of the objects in these lens populations determines the frequency of microlensing along that line of sight, which is characterized by a value known as the optical depth due to microlensing. (This is not to be confused with the more common meaning of optical depth, although it shares some properties.) The optical ...
View history; Tools. Tools. move to sidebar hide. ... Astrophysics is the branch of astronomy that deals with the physics of the ... Optical depth (astrophysics ...
The most powerful telescope to be launched into space has made history by detecting a record number of new stars in a distant galaxy. NASA's James Webb Space Telescope, history's largest and most ...
28 BCE – Chinese history book Book of Han makes earliest known dated record of sunspot. [34] c. 150 CE – Claudius Ptolemy completes his work Almagest, that codifies the astronomical knowledge of his time and cements the geocentric model in the West, and it remained the most authoritative text on astronomy for more than 1,500 years.