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The Baily's beads effect or diamond ring effect is a feature of total and annular
solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an eclipse season, approximately every six mon ...
s. As the
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
covers the
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
during a solar eclipse, the rugged topography of the lunar limb allows beads of
sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when ...
to shine through in some places while not in others. The effect is named after Francis Baily, who explained the phenomenon in 1836. The diamond ring effect is seen when only one bead is left, appearing as a shining "diamond" set in a bright ring around the lunar
silhouette A silhouette ( , ) is the image of a person, animal, object or scene represented as a solid shape of a single colour, usually black, with its edges matching the outline of the subject. The interior of a silhouette is featureless, and the silhou ...
.
Lunar topography Selenography is the study of the surface and physical features of the Moon (also known as geography of the Moon, or selenodesy). Like geography and areography, selenography is a subdiscipline within the field of planetary science. Historica ...
has considerable
relief Relief is a sculptural method in which the sculpted pieces are bonded to a solid background of the same material. The term '' relief'' is from the Latin verb ''relevo'', to raise. To create a sculpture in relief is to give the impression that th ...
because of the presence of
mountains A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher th ...
,
crater Crater may refer to: Landforms * Impact crater, a depression caused by two celestial bodies impacting each other, such as a meteorite hitting a planet * Explosion crater, a hole formed in the ground produced by an explosion near or below the surf ...
s,
valleys A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams ...
, 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
occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...
s of
star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
s. 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 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. T ...
, lasting 1–2 minutes. After the diamond ring effect has diminished, the subsequent Baily's beads effect and totality phase are safe to view without the solar filters used during the partial phases. By then, less than 0.001% of the Sun's
photosphere The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...
is visible. 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. 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 A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively. In the ...
(the Greek ''chrōma'' meaning "color") appears. Though the reddish hydrogen radiation is most visible to the
unaided eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection. Vision corrected to normal ...
, the chromosphere also emits thousands of additional
spectral line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to ident ...
s.


Observational history

Although Baily is often said to have discovered the cause of the feature which bears his name, Sir
Edmond Halley Edmond (or Edmund) Halley (; – ) was an English astronomer, mathematician and physicist. He was the second Astronomer Royal in Britain, succeeding John Flamsteed in 1720. From an observatory he constructed on Saint Helena in 1676–77, H ...
made the first recorded observations of Baily's beads during the solar eclipse of 3 May 1715.Great Britain did not adopt the
Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years d ...
until 1752, so at the time of the eclipse, the date was recorded as 22 April 1715.
Halley described and correctly ascertained the cause of the effect in his "Observations of the late Total Eclipse of the Sun .. in the ''
Philosophical Transactions of the Royal Society ''Philosophical Transactions of the Royal Society'' is a scientific journal published by the Royal Society. In its earliest days, it was a private venture of the Royal Society's secretary. It was established in 1665, making it the first journa ...
'': 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 Jedburgh (; gd, Deadard; sco, Jeddart or ) is a town and former royal burgh in the Scottish Borders and the traditional county town of the historic county of Roxburghshire, the name of which was randomly chosen for Operation Jedburgh in ...
in the
Scottish Borders The Scottish Borders ( sco, the Mairches, 'the Marches'; gd, Crìochan na h-Alba) is one of 32 council areas of Scotland. It borders the City of Edinburgh, Dumfries and Galloway, East Lothian, Midlothian, South Lanarkshire, West Lot ...
, he reported that:


In media

Cosmas Damian Asam Cosmas Damian Asam (29 September 1686 – 10 May 1739) was a German painter and architect during the late Baroque period. Born in Benediktbeuern, he lived in Rome from 1711 to 1713 to study at the Accademia di San Luca with Carlo Maratta. ...
was probably the earliest realistic painter to depict a total solar eclipse and diamond ring. His painting was finished in 1735. The Baily's beads phenomenon is seen during the credit opening sequence of the NBC TV show '' Heroes'', while the Diamond Ring effect is seen during the credit opening sequence of '' Star Trek: Voyager'', albeit from a fictitious extrasolar body, seen from space.


Gallery

Total Solar Eclipse 8-21-17 near Ravenna Nebraska 13.jpg, Diamond ring effect visible during the total
solar eclipse of August 21, 2017 The solar eclipse of August 21, 2017, dubbed the "Great American Eclipse" by the media, was a total solar eclipse visible within a band that spanned the contiguous United States from the Pacific to the Atlantic coasts. It was also visible as ...
, in
Ravenna, Nebraska Ravenna is a city in Buffalo County, Nebraska, United States. It is part of the Kearney, Nebraska Micropolitan Statistical Area. The population was 1,441 at the 2020 census. History Ravenna was founded in 1886 when the Burlington Railroad was ...
. (The diffraction spikes emanating tangentially from the diamond are an artifact of the camera optics, not a natural phenomenon.) Kamyzyak. Diamond Ring.ogv, The diamond ring effect during the
solar eclipse of March 29, 2006 A total solar eclipse occurred on March 29, 2006. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's a ...
, as seen from
Kamyzyak Kamyzyak (russian: Камызя́к; kk, Құмөзек, ''Qumózek'') is a town and the administrative center of Kamyzyaksky District in Astrakhan Oblast, Russia, located on the Kamyzyak River (a branch in the delta of the Volga), south of A ...
, Russia Solar Eclipse 8.21.17 Diamond Ring.jpg, The diamond ring effect as totality ends during the total solar eclipse of August 21, 2017, in central
Wyoming Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to t ...
. The rainbow coloration is a
lens flare A lens flare happens when light is scattered or flared in a lens system, often in response to a bright light, producing a sometimes undesirable artifact in the image. This happens through light scattered by the imaging mechanism itself, for ex ...
and not a natural phenomenon.


References


Notes


Citations


External links

* * {{DEFAULTSORT:Baily's Beads Eclipses Articles containing video clips