penumbra

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penumbra

(pĭnŭm`brə): 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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.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/

penumbra

(pi-num -bră)
1. See umbra.
2. See sunspots.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Penumbra

 

the space between regions of total shadow and total light formed behind an opaque body illuminated by a light source whose dimensions are comparable both with the dimensions

Figure 1

of the body and with the distance from the light source to the body (see Figure 1). Only part of the light source is visible in the penumbra; the light source is not visible in the umbra and is completely visible in the region of total light. The point of observation of a partial solar eclipse is within the penumbra formed by the moon as illuminated by the sun.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

penumbra

[pə′nəm·brə]
(astronomy)
The outer, relatively light part of a sunspot.
(optics)
That portion of a shadow illuminated by only part of a radiating source.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

penumbra

1. a fringe region of half shadow resulting from the partial obstruction of light by an opaque object
2. Astronomy the lighter and outer region of a sunspot
3. Painting the point or area in which light and shade blend
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
The entire spectacle will last five hours and 33 minutes, from the penumbral lunar phase until the end of the lunar eclipse.
Another nice feature is that all D-free penumbral connections are valid.
Inoue et al., "The growth rate of early DWI lesions is highly variable and associated with penumbral salvage and clinical outcomes following endovascular reperfusion," International Journal of Stroke, vol.
The first penumbral stage begins when the Moon's leading edge enters Earth's penumbra.
The trial hypothesized that patients with favorable neuroimaging "penumbral" pattern were more likely to achieve better outcome from IA treatment of AIS.
The group developed the number of small penumbral sunspots within it as it passed the CM on Aug 13 before reducing by Aug 15, however the total area of the group increased to 240 millionths.
This is called a penumbral eclipse and the occasions when the alignment is perfect are called an umbral eclipse.
Such penumbral eclipses often go unnoticed because the darkening is so slight.
(19) In any lunar eclipse, a "penumbral" period commences and concludes the eclipse, and this portion of an eclipse is either invisible or barely visible.
Among the topics explored are Yoder's systematic defense of Christian pacifism, postmodernity and his eschatological genealogy of morals, Yoder and Said on a politics of land and return, laughing with the world, and inheriting his radical democracy with the penumbral vision of Rowan Williams.
The only neuroprotective treatment known to save the penumbral tissue is intravenous thromblysis with tissue plasminogen activator (rTPA) within 3-4.5 hours.
The Moon's contact time with Earth's umbral and penumbral shadows from Delhi was in totality from 00:52 hours to 2:33 hours.