francies baily, may 15, 1836, baily's beads, blogs, today in science, space

Baily’s beads are beads of sunlight caused when sunlight shines between mountains and other features on the moon. These Baily’s beads are from the February 16, 1991, annular solar eclipse. Image via Fred Espenak, aka Mr Eclipse. Used with permission.

May 15, 1836: On this date in science, Francis Baily (1774-1844), an English astronomer, saw beads of sunlight shining along the edge of the moon’s silhouette during an eclipse of the sun.

It was an annular eclipse – nowadays often called a ring of fire eclipse – meaning that the moon was too far away in its monthly orbit around Earth to appear large enough in our sky to cover the sun completely.  Baily saw beads of light shining around the darkened lunar limb.

francies baily, may 15, 1836, baily's beads, blogs, today in science, space

Another shot of Bailey’s beads from the February 16, 1999, eclipse. Image via Fred Espenak. Used with permission.

Baily’s discovery

Baily’s goal was to time the length of the annular phase of the eclipse. He would do this by recording the time during which the moon was inside the sun’s disk. He would start timing as soon as a line of sunlight appeared along the trailing edge of the moon.

Baily expected to observe a nice, smooth line of sunlight along one edge of the moon. Imagine his surprise as he watched and waited for it to appear – while looking through a filtered 2.6-inch, f/16 refractor – at 40 magnification. Instead of seeing a smooth line of sunlight, he saw a broken line of light and dark spots.

Don’t start that stopwatch yet, Mr. Baily!

Baily and others have commented that the line of light and dark spots resembled beads on a string. And, as the seconds ticked by, Baily saw the dark spots decrease in both number and size. And he saw the light spots increase in both number and size, until there was a fine line of sunlight around the edge of the moon.

Okay, now start the stopwatch!

But after the moon was completely inside the solar disk, the moon did look “smooth and circular” to him. At least four other local observers confirmed this observation during this eclipse.

Sunlight shining through lunar valleys

Later, others realized that these beads of light appeared due to mountains and valleys, crater walls, and other topographic features extending above the limb, or edge, of the moon as seen from Earth. This phenomenon earned the name Baily’s beads. And you can see it during total eclipses, too, just before the moon covers the sun completely. A video of Baily’s beads is here.

Baily published his discovery in the Monthly Notices of the Royal Astronomical Society in December of that year. In a talk to the Royal Astronomical Society, he mentioned that he knew of only one other person who had seen these before, that being M Van Swiniden (1746–1823), a Dutch scientist.

Today, Baily’s beads are one of the eclipse effects that amateur astronomers around the world – using proper eye protection – watch for during annular and total eclipses of the sun.

francies baily, may 15, 1836, baily's beads, blogs, today in science, space

Francis Baily, for whom Baily’s beads are named. Image via Wikimedia Commons.

Baily’s beads during a total eclipse

Baily discovered the beads during an annular eclipse, but they’re best known for being visible during a total eclipse. Let’s look at the process during a total eclipse.

During a total eclipse, the moon moves across a sun that takes up the same amount of sky. As the leading edge of the moon moves toward covering the remainder of the sun, dark spots interrupt the last bit of sunlight. Those are lunar mountains. Totality has not yet begun, as sunlight is still peeking between these dark spots.

As the seconds tick by, the sunlight decreases, and the dark areas increase until there is only one spot of light on the limb of the moon: the diamond ring. When that final bright spot disappears, the total eclipse begins. Remove the solar filters for a fantastic view.

As the total phase draws to a close, the effects resume in reverse order. On the trailing side of the moon the sunlight appears. First, the diamond ring. Next, Baily’s beads. Watch a video of Baily’s beads during the August 21, 2017, total eclipse here.

The Baily’s beads phase is unappreciated during total eclipses. The main show is totality, and observers are typically preparing to remove their solar filters while Baily’s beads and the diamond ring are occurring. And those Baily’s beads at the end of totality? They are accompanied by sighs as the total phase comes to an abrupt end. But you can watch the phenomena at the end of the total eclipse with unfiltered and dark-adapted eyes, so they might appear brighter and more noteworthy than those leading into the total phase.

francies baily, may 15, 1836, baily's beads, blogs, today in science, space

Baily’s beads, visible during a total eclipse of the sun. Here, you’re almost seeing another effect, known as the diamond ring effect. Image via Luc Viatour/ Encyclopedia Britannica.

Baily’s beads during an annular eclipse

Here is the process during an annular eclipse, the type that Baily saw. To start, the moon appears smaller than the sun, so you must use filters the entire time. At the center of the annular eclipse, you see a ring of the sun around the moon. And the episode begins on the trailing not the leading edge of the moon. As the last bit of the moon moves onto the sun, the uneven dark limb of the moon produces bright spots. These bright spots increase in number and size until the whole lunar limb is a bright arc of sunlight.

That is what Baily saw. Toward the end of the annular phase of the eclipse, now looking toward the leading edge of the moon, that bright arc of sunlight begins to be interrupted by dark spots, growing in size. A video of Baily’s beads during an annular eclipse is here.

Extending the beads

Is there a way to make those beads visible for a longer length of time? Yes, there are two ways. One is to hop onto a jet and zoom along the path of the eclipse. This will also extend the length of the total phase of the eclipse.

The other way is to set up near the edge of the central path of the eclipse. The typical eclipse shows the main event, whether annular or total, only along a path on the earth that is about 100 miles (160 km) wide. Sit in the center of that path and the eclipse phase will last longer than near the north or south limit of this path. But if you go near the north or south limit, the Baily’s beads phase will last longer, at the sacrifice of the central phase. A video of Baily’s beads lasting more than two minutes is here.

francies baily, may 15, 1836, baily's beads, blogs, today in science, space

Petr Horalek took these images from the La Silla Observatory in Chile during the July 2, 2019, total eclipse. He was near the edge of the path of totality. Image via Petr Horalek. Used by permission.

Baily’s beads or Halley’s beads?

On April 22, 1715 (Julian calendar, or May 3, 1715, Gregorian calendar) Edmond Halley (1656 – 1742) observed a total solar eclipse from London. He predicted the eclipse, and so it is often referred to as Halley’s Eclipse. During this total eclipse, Halley observed Baily’s beads too, 59 years before Baily was even born. Here is Halley’s description:

About two Minutes before the Total Immersion, the remaining part of the Sun was reduced to a very fine Horn, whose Extremeties seemed to lose their Acuteness, and to become round like Stars … which Appearance could proceed from no other Cause but the Inequalities of the Moon’s Surface, there being some elevated parts thereof near the Moon’s Southern Pole, by whose Interposition part of that exceedingly fine Filament of Light was intercepted.

This is an excellent description of Baily’s beads, even though Halley hit the “shift” key a few too many times!

Edmond Halley was the first to observe and identify the event we now call Baily’s beads, yet they are not named after him. What is named after Edmond Halley?

Halley’s Comet, which he did not discover, but he did predict its return.
Halley’s Eclipse in 1715, which he also predicted.
Halley, the crater on the moon, named long after Halley passed away.
Halley, the crater on Mars, named in 1973.
Halley Research Station, in Antarctica, established in 1956. Edmond Halley never went to Antarctica, nor to the moon nor Mars, for that matter.
Halley’s Mount, a hill on the island of Saint Helena, from where Halley observed the southern sky.

But we don’t have Halley’s beads, even though he discovered and defined them. One suggestion is to refer to the beads seen during the annular eclipses as Baily’s beads and the ones seen during the total eclipses as Halley’s beads. Then Edmond Halley would finally be recognized for something he discovered.

Bottom line: May 15, 1836: Francis Baily, an English astronomer, saw light shining through lunar ridges during an eclipse of the sun. These are now known as Baily’s beads.

Twitter10Facebook2BufferShare

TECH NEWS RELATED

HP Reverb G2 review

If you think of the big names that are vying for a slice of the VR pie, HP probably isn’t the first one that jumps into your mind. HTC and Valve were certainly the pioneers in the space and both are still enjoying huge success, while Facebook/Meta/whatever they’re calling themselves ...

View more: HP Reverb G2 review

Potential new meteor shower is 'all or nothing event,' says NASA astronomer

A shattering comet might generate a new tau Herculids shower on May 30 and 31.

View more: Potential new meteor shower is 'all or nothing event,' says NASA astronomer

Elon Musk’s net worth falls below $200 billion amid TSLA’s recent slump

Tesla shares have recently hit 11-month lows, and with it, CEO Elon Musk’s net worth has dropped below $200 billion. Musk has lost about $77.6 billion of his net worth year-to-date.  Musk’s wealth is in no small part tied to his ownership of electric vehicle maker Tesla, which he ...

View more: Elon Musk’s net worth falls below $200 billion amid TSLA’s recent slump

Tesla (TSLA) stock way oversold, Twitter overhang way overdone: Wedbush analyst

Tesla stock (NASDAQ:TSLA) recently fell to an 11-month low, with shares dropping almost 7% on Tuesday. Despite this, Wedbush analyst Dan Ives believes that Tesla stock is way oversold and concerns about CEO Elon Musk’s acquisition of Twitter are getting way overdone. When Elon Musk announced that he had ...

View more: Tesla (TSLA) stock way oversold, Twitter overhang way overdone: Wedbush analyst

Tesla drivers are almost 50% less likely to crash while driving a Tesla than when driving other cars: study

New research from Cambridge Mobile Telematics (CMT), one of the industry’s largest telematics service providers, has found several interesting trends regarding electric vehicle drivers. Among the study’s findings involved Tesla drivers, who were almost 50% less likely to crash while driving a Tesla than when driving other cars. CMT’s ...

View more: Tesla drivers are almost 50% less likely to crash while driving a Tesla than when driving other cars: study

China's world Big Data Expo 2022 to boost global digital economy

A poster for Big Data Expo 2022. /China Media Group In 2022, China ranked as one of the best in computing power among major economies, according to a recent industry report which highlighted the country’s impressive advances in the field, noting that such high-end power has become the driving ...

View more: China's world Big Data Expo 2022 to boost global digital economy

Researchers start breeding 12,000 space seeds returned by Shenzhou-13

The re-entry module of the Shenzhou-13 manned spacecraft successfully lands at Dongfeng landing site in north China’s Inner Mongolia Autonomous Region, April 16, 2022. /CFP Chinese researchers have commenced breeding experiments on 12,000 seeds – including alfalfa, oats and fungi – that were bred inside the Shenzhou-13 crewed spaceship ...

View more: Researchers start breeding 12,000 space seeds returned by Shenzhou-13

Formation of carbonatite magmas decrypted

Geoscientists Jasper Berndt (left) and Stephan Klemme present a volcanic rock from Lake Laach. This Eifel rock contains the mineral Hauyn (about 0.5 mm), in which the researchers found the microscopic carbonatite melt inclusions (small picture below left). In the background is the ’Jeol electron beam microprobe’ with which ...

View more: Formation of carbonatite magmas decrypted

Almost Lights Out: See NASA’s InSight Mars Lander’s Final Selfie

Launcher wins Space Force contract to support engine development

5 ways to save money when buying photography equipment

North Korea testing 'nuclear detonation device': Seoul

Advanced Air Mobility aims to shorten travel time

How Webb will explore our own solar system

Hubble telescope spots enormous elliptical galaxy surrounded by mysterious shells

Researchers start planting space-bred seeds returned by Shenzhou-13

OneWeb and TinSky complete first West African LEO Satellite Gateway

NASA-supported solar sail could take science to new heights

CubeSat set to demonstrate NASA's fastest laser link from space

Polar Ice and Snow monitoring mission CRISTAL on track

OTHER TECH NEWS

Top Car News Car News