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An observer in the penumbra experiences a partial eclipse. An alternative definition is that the penumbra is the region where some or all of the light source is obscured (i.e., the umbra is a subset of the penumbra). For example, NASA's Navigation and Ancillary Information Facility defines that a body in the umbra is also within the penumbra. [2]
The moon’s penumbra causes partial solar eclipses. The super blood moon lunar eclipse occurred late in the night of Sunday, Jan. 20, 2019, and carried over into early morning Monday.
Umbra, penumbra and antumbra. A point source of light casts only a simple shadow, called an "umbra". For a non-point or "extended" source of light, the shadow is divided into the umbra, penumbra, and antumbra. The wider the light source, the more blurred the shadow becomes. If two penumbras overlap, the shadows appear to attract and merge.
The umbra may be surrounded completely or only partially by a brighter region known as the penumbra. [23] The penumbra is composed of radially elongated structures known as penumbral filaments and has a more inclined magnetic field than the umbra. [24] Within sunspot groups, multiple umbrae may be surrounded by a single, continuous penumbra.
The penumbra causes a subtle dimming of the lunar surface, which is only visible to the naked eye when the majority of the Moon's diameter has immersed into Earth's penumbra. [8] A special type of penumbral eclipse is a total penumbral lunar eclipse, during which the entire Moon lies exclusively within Earth's penumbra. Total penumbral eclipses ...
Diagram of the Wilson effect. The umbra is the darker inner circle and the penumbra is the lighter ring around the umbra. In astronomy, the Wilson effect is the perceived depression of a sunspot's umbra, or center, in the Sun's photosphere. The magnitude of the depression for the umbra is between 500 and 1000 km, with an average of 600 km. [1]
A total solar eclipse occurs when the Earth intersects the umbra portion of the Moon's shadow. When the umbra does not reach the surface of the Earth, the Sun is only partially occulted, resulting in an annular eclipse. Partial solar eclipses occur when the viewer is inside the penumbra. [14]
Since Earth's diameter is 3.7 times the Moon's, the length of the planet's umbra is correspondingly 3.7 times the average distance from the Moon to the Earth: roughly 1,400,000 km (870,000 mi). The width of the Earth's shadow at the distance of the lunar orbit is approximately 9000 km (~ 2.6 lunar diameters), which allows people of the Earth to ...