The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast.
Umbra, penumbra and antumbra of Earth and images that could be seen at some points in these areas (note: the relative size and distance of the bodies shown are not to scale).Umbra (A) and penumbra (B)
These names are most often used for the shadows cast by celestial bodies, though they are sometimes used to describe levels, such as in sunspots.
Umbra, penumbra, and antumbra formed through windows and shutters
The umbra (Latin for "shadow") is the innermost and darkest part of a shadow, where the light source is completely blocked by the occluding body. An observer within the umbra experiences a total occultation. The umbra of a round body occluding a round light source forms a right circular cone. When viewed from the cone's apex, the two bodies appear the same size.
The distance from the Moon to the apex of its umbra is roughly equal to that between the Moon and Earth: 384,402 km (238,856 mi). Since Earth's diameter is 3.7 times the Moon's, its umbra extends correspondingly farther: roughly 1.4 million km (870,000 mi).[1]
The penumbra (from the Latin paene "almost, nearly") is the region in which only a portion of the light source is obscured by the occluding body. 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]
Scale diagram of Earth's shadow, showing how the umbral cone extends beyond the orbit of the Moon (the Moon is indicated by the yellow dot).Earth's umbra, as seen during a partial lunar eclipse
AntumbraEdit
Transit of Mercury in front of the Sun, an extreme version of an annular eclipse. Mercury is visible as a black dot below and to the left of the center. The dark area above the center of the solar disk is a sunspot.
The antumbra (from Latin ante, "before") is the region from which the occluding body appears entirely within the disc of the light source. An observer in this region experiences an annular eclipse, in which a bright ring is visible around the eclipsing body. If the observer moves closer to the light source, the apparent size of the occluding body increases until it causes a full umbra.[3]
^Pogge, Richard. "Lecture 9: Eclipses of the Sun & Moon". Astronomy 161: An Introduction to Solar System Astronomy. Ohio State University. Retrieved July 16, 2015.
^Event Finding Subsystem Preview Navigation and Ancillary Information Facility.
^"Eclipses: What Is the Antumbra?". timeanddate.com. Retrieved 26 May 2019.
umbra, penumbra, antumbra, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, . This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Umbra penumbra and antumbra news newspapers books scholar JSTOR December 2012 Learn how and when to remove this template message The umbra penumbra and antumbra are three distinct parts of a shadow created by any light source after impinging on an opaque object Assuming no diffraction for a collimated beam such as a point source of light only the umbra is cast Umbra penumbra and antumbra of Earth and images that could be seen at some points in these areas note the relative size and distance of the bodies shown are not to scale Umbra A and penumbra B These names are most often used for the shadows cast by celestial bodies though they are sometimes used to describe levels such as in sunspots Contents 1 Umbra 2 Penumbra 3 Antumbra 4 See also 5 ReferencesUmbra Edit Umbra redirects here For other uses see Umbra disambiguation nbsp Umbra penumbra and antumbra formed through windows and shuttersThe umbra Latin for shadow is the innermost and darkest part of a shadow where the light source is completely blocked by the occluding body An observer within the umbra experiences a total occultation The umbra of a round body occluding a round light source forms a right circular cone When viewed from the cone s apex the two bodies appear the same size The distance from the Moon to the apex of its umbra is roughly equal to that between the Moon and Earth 384 402 km 238 856 mi Since Earth s diameter is 3 7 times the Moon s its umbra extends correspondingly farther roughly 1 4 million km 870 000 mi 1 Penumbra Edit Penumbra redirects here For other uses see Penumbra disambiguation The penumbra from the Latin paene almost nearly is the region in which only a portion of the light source is obscured by the occluding body 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 nbsp Scale diagram of Earth s shadow showing how the umbral cone extends beyond the orbit of the Moon the Moon is indicated by the yellow dot nbsp Earth s umbra as seen during a partial lunar eclipseAntumbra Edit nbsp Transit of Mercury in front of the Sun an extreme version of an annular eclipse Mercury is visible as a black dot below and to the left of the center The dark area above the center of the solar disk is a sunspot The antumbra from Latin ante before is the region from which the occluding body appears entirely within the disc of the light source An observer in this region experiences an annular eclipse in which a bright ring is visible around the eclipsing body If the observer moves closer to the light source the apparent size of the occluding body increases until it causes a full umbra 3 See also EditAntisolar point Earth s shadowReferences Edit Pogge Richard Lecture 9 Eclipses of the Sun amp Moon Astronomy 161 An Introduction to Solar System Astronomy Ohio State University Retrieved July 16 2015 Event Finding Subsystem Preview Navigation and Ancillary Information Facility Eclipses What Is the Antumbra timeanddate com Retrieved 26 May 2019 Portals nbsp Physics nbsp Astronomy nbsp Stars nbsp Spaceflight nbsp Outer space nbsp Solar System nbsp Science Retrieved from https en wikipedia org w index php title Umbra penumbra and antumbra amp oldid 1155048357 Penumbra, wikipedia, wiki, book, books, library,
