umbra

(redirected from umbras)
Also found in: Dictionary, Thesaurus, Medical, Acronyms.
Related to umbras: umbral

umbra:

see eclipseeclipse
[Gr.,=failing], in astronomy, partial or total obscuring of one celestial body by the shadow of another. Best known are the lunar eclipses, which occur when the earth blocks the sun's light from the moon, and solar eclipses, occurring when the moon blocks the sun's light
..... Click the link for more information.
; sunspotssunspots,
dark, usually irregularly shaped spots on the sun's surface that are actually solar magnetic storms. The spots are darker because the temperature of the spots is lower than that of the surrounding photosphere (the visible surface of the sun).
..... Click the link for more information.
.
Umbral and penumbral regions of a shadowclick for a larger image
Umbral and penumbral regions of a shadow

umbra

(um -bră)
1. The dark inner region of a shadow cast by an object illuminated by a light of finite size rather than a pinpoint of light. The less dark outer region of the shadow is the penumbra (see illustration). The source of light is totally obscured to someone in the umbral region but only partly obscured in the penumbral region. See eclipse.
2. See sunspots.

umbra

[′əm·brə]
(astronomy)
The dark, central region of a sunspot.
(optics)
That portion of a shadow which is screened from light rays emanating from any part of an extended source.

umbra

1. a region of complete shadow resulting from the total obstruction of light by an opaque object, esp the shadow cast by the moon onto the earth during a solar eclipse
2. the darker inner region of a sunspot
References in periodicals archive ?
High tropospheric clouds, or cirrus, will also dim the umbra except near its edge; this is evident when comparing the Clear red-light curve with the Cirrus clouds curve.
Since weather is not the same everywhere around the Earth's limb, the umbra can display dark and bright patches.
That is, the puns on umbra and capra are not so very surprising in a poet who enjoys stretching and playing with meanings not only of everyday prosaic words(21) but even, more playfully, of personal names.
Umbra is a GPU accelerated rendering optimization middleware available for PC, Xbox360 and PS3.