limb darkening

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Related to limb darkening: limb brightening

limb darkening:

see sunsun,
intensely hot, self-luminous body of gases at the center of the solar system. Its gravitational attraction maintains the planets, comets, and other bodies of the solar system in their orbits.
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limb darkening

The decrease in intensity at visible wavelengths from the center to the limb of the Sun's disk. Light from the central portion of the disk is radiated radially toward us, whereas light from closer to the limb has to pass obliquely through a greater thickness of the solar atmosphere. For a given limit of penetration we can therefore see deeper into the photosphere at the center of the disk than at the limb, where our line of sight passes through cooler gases. The limb consequently appears less bright.

Limb darkening has been detected in other stars, principally by the use of three-color photometry of the light curves of eclipsing binaries (the effect being more pronounced in blue light than in red) and by speckle interferometry.

A similar effect is observed in planets with deep atmospheres, notably Jupiter and Saturn, and arises from the scattering of sunlight by atmospheric particles.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

limb darkening

[′lim ‚där·kə·niŋ]
An observed darkening near the surface of the sun's limb as compared to its brighter center.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
In the end, the simplest explanation for limb darkening lies in the recognition that directional spectral emissivity occurs naturally within condensed matter [66, 71-73].
Limb darkening revealed that the solar photosphere was condensed, but not highly metallic.
As sub-components of the photosphere, the same mechanism invoked to understand limb darkening [section]2.3.2 can be used to explain granular emissivity.
Today, limb darkening constitutes a central pillar of the gaseous solar models.
As such, higher spatial resolution on granules may soon reveal that they individually exhibit the same features as observed globally in limb darkening. This would be expected if the emissivity of the Sun simply reflected the constitution of its condensed surface.
Titan's limb darkening is strikingly obvious in the beautiful series of images they obtained.
The eminent British planetary observer David Gray has been able to convincingly replicate Comas Sola's more difficult observation of Titan's limb darkening against a dark sky background.
Chapter 3 deals with techniques for observing sunspots, granulation, limb darkening, and faculae.
My 31-page booklet, Observer's Guide to the Transit of Mercury, 1999 Nov 15, has much more information about this event, including details of limb darkening at various wavelengths, maps of weather prospects and transit circumstances, a 38-item bibliography, and detailed predictions for 192 locations worldwide.
In addition to making it possible to view small sunspots, binoculars will show the limb darkening with greater ease than the naked eye alone.
Limb darkening really helps faculae stand out against the photosphere.