Английская Википедия:Baily's beads
Шаблон:Short description Шаблон:Multiple image The Baily's beads effect, and diamond ring, and, more rarely, double diamond ring, effects[1] are features of total and annular solar eclipses. Although caused by the same phenomenon, they are distinct events during these types of solar eclipses. As the Moon covers the Sun during a solar eclipse, the rugged topography of the lunar limb allows beads of sunlight to shine through in some places while not in others. The effect is named after Francis Baily, who explained the phenomenon in 1836.[2][3] The diamond ring effects are seen when only one or two beads are left, appearing as shining "diamonds" set in a bright ring around the lunar silhouette.[4]
Lunar topography has considerable relief because of the presence of mountains, craters, valleys, and other topographical features. The irregularities of the lunar limb profile (the "edge" of the Moon, as seen from a distance) are known accurately from observations of grazing occultations of stars. Astronomers thus have a fairly good idea which mountains and valleys will cause the beads to appear in advance of the eclipse. While Baily's beads are seen briefly for a few seconds at the center of the eclipse path, their duration is maximized near the edges of the path of the umbra, lasting 1–2 minutes.
It is not safe to view Baily's beads or the diamond ring effect without proper eye protection because in both cases the photosphere is still visible.[5]
Observers in the path of totality of a solar eclipse see first a gradual covering of the Sun by the lunar silhouette for just a small duration of time from around one minute to four minutes, followed by the diamond ring effect (visible without filters) as the last bit of photosphere disappears. As the burst of light from the ring fades, Baily's beads appear as the last bits of the bright photosphere shine through valleys aligned at the edge of the Moon.[6] As the Baily's beads disappear behind the advancing lunar edge (the beads also reappear at the end of totality), a thin reddish edge called the chromosphere (the Greek chrōma meaning "color") appears. Though the reddish hydrogen radiation is most visible to the unaided eye, the chromosphere also emits thousands of additional spectral lines.[7]
Observational history
(2 July 2019)[1]
Although Baily is often said to have discovered the cause of the feature which bears his name, Sir Edmond Halley made the first recorded observations of Baily's beads during the solar eclipse of 3 May 1715.[8][Note 1] Halley described and correctly ascertained the cause of the effect[8] in his "Observations of the late Total Eclipse of the Sun [...]" in the Philosophical Transactions of the Royal Society:
The term "Baily's beads" then came into use after Baily described the phenomenon to the Royal Astronomical Society in December 1836. Having observed the solar eclipse of 15 May 1836 from Jedburgh in the Scottish Borders, he reported that:
In media
In 1735, painter and architect Cosmas Damian Asam completed a painting that is probably the earliest known work that realistically depicts a total solar eclipse and diamond ring.[9]
The Diamond Ring effect is seen during the credit opening sequence of Star Trek: Voyager (1995-2001), albeit from a fictitious extrasolar body, as seen from space.Шаблон:Fact
The Baily's beads phenomenon is seen during the credit opening sequence of the NBC TV show Heroes (2006-2010).Шаблон:Fact
Gallery
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Diamond ring effect visible during the total solar eclipse of August 21, 2017, in Ravenna, Nebraska. (The diffraction spikes emanating tangentially from the diamond are an artifact of the camera optics, not a natural phenomenon.)
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The diamond ring effect during the solar eclipse of March 29, 2006, as seen from Kamyzyak, Russia
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The diamond ring effect as totality ends during the total solar eclipse of August 21, 2017, in central Wyoming. The rainbow coloration is a lens flare and not a natural phenomenon.
References
Notes
Citations
External links
- ↑ 1,0 1,1 Шаблон:Cite news
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite book
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite web
- ↑ Pasachoff, J. M. & Covington, M. The Cambridge Eclipse Photography Guide (Cambridge Univ. Press, 1993)Шаблон:Page needed
- ↑ Шаблон:Cite journal
- ↑ 8,0 8,1 Ошибка цитирования Неверный тег
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