umbra


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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
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; 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).
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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 ?
The third stage is total eclipse, beginning when the last rim of Moon slips into the umbra.
The Trina Turk, MaryJane's Home and Umbra presentations marked a huge step in Peking Handicraft's progression as a soft-home resource, according to CEO Mark Grand.
By focusing on the next hot item, Umbra has broken many of the rules about product assortments, distribution and category specialization.
This time around a high speed chase would not be necessary as the speed of the Umbra shadow over Gulf of Khambhat begins with Mach 50-60 slowing down to Mach 20 near Bhopal," said Dr.
Unlike Richard Miller, who contended that all 19th- and 20th-century African American cultural expressions have been alternative or tangential to the "mainstream" values of the United States (201-02), Oren pointed out that Umbra was a self-consciously innovative gesture made by alienated young men exploring a bohemian lifestyle.
When the moon was completely in the umbra, the full aperture was used; however, when only part of the moon was in the umbra, the aperture was reduced to about 0.
This second edition has newer poems that continue to showcase Thomas's energy and intelligence, including a lovely poem written in memory of Tom Dent, the political activist, poet and cofounder of the Umbra Workshop.
Budding card sharks will love these adorable Umbra Splish Splash playing cards ($5 per deck, umbra.
Umbra Cuscinetti, an East Granby, CT-based arm of the Umbra Group, has created ballscrews for electromechanical injection molding machines.
Long, thin filaments radiate from the umbra into a brighter surrounding region called the penumbra.
The path of the moon's umbra (the darkest central portion of the long, tapering lunar shadow caused by the passing of the moon between the earth and the sun which crosses our planet at twice the speed of sound), will begin in the south Atlantic Ocean at sunrise.
Key words: Anax; behavior; competition; leopard frog; morphology; phenotypic plasticity, predation; Rana pipiens; Rana sylvatica; Umbra limi; wood frog.