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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.

penumbra

(pi-num -bră)
1. See umbra.
2. See sunspots.

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.

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.

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
References in periodicals archive ?
2014 from the ABSA forward hedging contract at the Penumbra Coal Mine.
When the sunspot is in the last phase of dissolution, the penumbra is less regularly radiated, and it seems formed of the thinnest and most tenuous part of the photosphere itself.
While it is currently common practice to administer IV TPA to those patients with a stroke-onset-to-treatment interval of <3 hours, thrombolytic therapy is probably not warranted in patients in whom penumbra volume does not significantly exceed the infarction core, as reperfusion hemorrhage risk outweighs the possible clinical outcome improvement likely to result from the salvage of a very modest tissue volume (Figure 4).
Triple H therapy is useful in treating delayed ischemic neurological deficit caused by the ischemic penumbra.
A palette of bold red, blue, green and gold - hues commonly used in vernacular buildings - invigorates the penumbra, bringing life and colour to the cool, luminous spaces.
He illustrates multiple views and numerous details of unknown or little known objects, many from the penumbra of the Michelangelo corpus.
In the device-based IA intervention subset, The Penumbra Aspiration Thrombectomy System showed 84.
to the debt financing for the Penumbra Coal Mine) being ongoing and
The October full moon will become dimmer and lose part of its southern rim as the Sun and Earth align, consigning the moon into our planet's shadowy penumbra.
Penumbra is an innovative Scottish mental health charity, Providing a wide range of services offering hope and practical steps towards recovery.
The penumbra does not cause any noticeable darkening of the Moon's surface, though some may argue it turns a little yellow.
It won't be passing through the darkest part of Earth's shadow - the umbra- but through the half-shadow either side of this - the region of half-light-half shadow called the penumbra.