Sun's Outer Atmosphere Revealed By Total Solar Eclipse Sun's Outer Atmosphere Revealed By Total Solar Eclipse By Tariq Malik, Space.com Managing Editor | July 16, 2010 12:06pm ET MORE The atmosphere of the sun blazes clearly in a new image from NASA that combines observations from Earth and space during the only total solar eclipse of this year. The new solar eclipse photo used observations from two NASA space telescopes and ground-based astronomers from Williams College in Massachusetts to assemble a detailed look at the sun's ultra-hot corona when the moon completely blocked the sun during the July 11 total solar eclipse . "The sky was wonderful," Williams College astronomer Jay Pasachoff told SPACE.com after the eclipse. Pasachoff led a Williams team that ventured to the remote Easter Island in the southern Pacific Ocean to study the sun's corona during the solar eclipse. [2010 Total Solar Eclipse Photos] Atmosphere of the sun The corona is the outer atmosphere of the sun and can be seen only during solar eclipses .

While the surface of the sun is typically about 10,000 degrees Fahrenheit (5,538 degrees Celsius), the gas in the corona can be up to 100 times hotter. During a total eclipse, when the disk of the sun is entirely blocked by the moon, the corona is suddenly visible as bright, wispy tendrils that can be safely viewed with the naked eye. (Protective glasses are required to watch the phases of the eclipse before and after totality. Viewing the sun?s disk directly can cause permanent eye damage.) Sun's corona revealed The NASA photo of the July 11 solar eclipse is a mosaic of three images layered on top of each other. The photo's outer ring in red is a false-color view of the sun's outer corona recorded by the LASCO instrument on the SOHO space observatory (a joint project of NASA and the European Space Agency), which observes the sun at a stable point in space between the star and Earth. LASCO is a coronagraph that uses a disk to blot out the sun and inner corona so its faint outer corona can be observed.

Pasachoff's observing team took the gray-and-white image that makes up the eclipse photo's middle ring. The corona's tendrils are easily visible in this ring stretching out away from the sun. In place of the moon at the center of the new image, NASA has added a view of the sun's surface as seen by the space agency's powerful Solar Dynamics Observatory (SDO). The SDO photo is actually an extreme ultraviolet light view of the sun, but was taken at about the same time as the others that make up the solar eclipse mosaic. The July 11 solar eclipse was the only total solar eclipse for this year, but it was actually the second solar eclipse to occur in 2010. An annular solar eclipse, in which the sun was not completely covered by the moon, occurred on Jan. 15. The total eclipse was touted as one of the most remote solar eclipses ever because it occurred over a hard-to-reach swath of the Pacific Ocean, visible on only a few islands and part of South America. "An impossible eclipse at the end of the world," said skywatcher Daniel Fischer, who watched the solar eclipse from the Patagonia region of Argentina as the sun set behind the Andes mountains.

The next total solar eclipse will occur in November 2012. Photos: Total Solar Eclipse of 2010 Definition of Corona of the Sun – Corona Atmospheric Layer of the Sun – PlanetFacts.org The Moon Corona In astronomy, corona is used to refer to the outer most area of the sun. In layman’s terms the corona is the proper name for the sun’s atmosphere. While significantly different from planetary atmospheres that refer to the air or gases that surround the planet due to gravity, the sun’s corona is generally held to be made out of plasma instead of regular gases. The corona is visible to the naked eye during solar eclipse. The halo of light that is visible around the moon during an eclipse is the corona. The corona is also the subject of scientific mystery since the corona is observed to be actually several times hotter than the surface of the sun. This observation has lead to divergent theories to explain this unusual difference in temperature. The corona is also known to form arches of plasma known as coronal loops. This is due to the reaction of the ionized gases to the suns magnetic field.

The corona sometimes ejects a portion of itself from the sun causing coronal material to shoot away from the sun in very high speed. Such phenomenon is called a coronal mass ejection. Another unique thing about the corona is that it doesn’t always cover all the sun, periodically the “poles” of the sun is not covered by the corona. What to See During an Eclipse | Exploratorium Past Eclipses What to See During an Eclipse As the moon passes in front of the sun, the eclipse goes through stages that provide an evolving spectacle, two-plus hours of steadily changing views. Click on the images to see what you can see. Remember: NEVER view any stage except totality with your naked eyes. Use safe viewing techniques to preserve your eyesight. Full Sun Before the eclipse begins, and after it ends, the full disk of the sun burns in the sky. The visible region of the sun is called the photosphere. While you wait for the eclipse to begin, use safe viewing techniques to look for sunspots, slightly cooler areas on the sun (only 4,500 degrees Celsius!) that look dark compared to the blinding photosphere. The sun has an eleven-year cycle of sunspot activity.

In 2016, we’re mid-way through the cycle, so the sun is showing a medium number of sunspots. You can’t see the moon as it approaches the sun, because from Earth we’re seeing its dark side—the New Moon. But it’s there, as will become obvious at First Contact. First Contact The eclipse begins at the moment the moon first “touches” the edge of the solar disk, approaching it from the left. (It doesn’t actually touch the sun, of course—but it appears to as it begins to pass in front of the solar disk.) This picture was taken with a 300-mm lens with a Calcium-K filter. (Photo by Eric Blackhurst, OPT) The moon, invisible until now in the daytime sky, becomes visible as a black disk blocking the sun. For the next hour and a half, it slowly consumes a larger and larger chunk of the sun. Partial Eclipse This image of the partially eclipsed sun looks purplish because of the filter on the telescope. It was taken using a Calcium-K filter, which sees the sun in near-ultraviolet light. Photo by Eric Blackhurst, OPT Second Contact Second contact occurs when the moon almost completely covers the sun, in the moments before totality.

The last bright flash of the sun, combined with an emerging view of the corona encircling the moon, produces a spectacular effect called the Diamond Ring. This image was taken with a 300-mm lens in white light. (Photo by Eric Blackhurst, OPT) You may see bright pink spots near the “diamond.” These are gigantic jets and loops of gas that rise from the sun’s surface, usually near sunspots. Called prominences, their beautiful hue is the color of glowing hydrogen gas. Totality The sun is now completely hidden, revealing the full glory of the solar corona. These few minutes of the total solar eclipse are the only times we on Earth can see the corona, the sun’s upper atmosphere, which streams out into space above the sun’s surface. Normally, the corona’s delicate light is outshone by the bright photosphere. This image was taken with a 600-mm lens in white light. (Photo by Eric Blackhurst, OPT) This is the one time you can safely look at the sun with your naked eye. If you can draw your eyes away from the sun for a few moments, you’ll notice that the sky has become quite dark and the temperature has dropped, comparable to twilight.

In the sky, the brighter stars and planets have come out. The horizon is lit up all around you, like a 360-degree sunset, where the Earth is experiencing a partial eclipse. Third Contact Totality ends at Third Contact, as the leading edge of the moon begins to move off the sun. On the moon’s trailing edge, the first light of the photosphere shines through mountains and valleys on its surface, creating a necklace-like effect called Bailey's Beads. At totality’s end, resume using safe viewing techniques . This image was taken with a 600-mm lens in white light. (Photo by Eric Blackhurst, OPT) Sunlight Restored Moments after Third Contact, the sun reemerges in a burst of light, creating a second Diamond Ring on the opposite side of the sun. As the moon reveals more of the sun, the corona quickly fades from view in the brightness of the newly restored photosphere. This image was taken with a 300-mm lens in white light. (Photo by Eric Blackhurst, OPT) Fourth Contact The eclipse is now nearly over. Fourth Contact, when the outer edge of the moon last touches the sun, marks its end.

From First Contact to this moment takes about two and a half hours. This picture was taken with a 300-mm lens with a Calcium-K filter. (Photo by Eric Blackhurst, OPT) Unraveling the Mystery of the Sun’s Superhot Atmosphere | UMass Lowell Unraveling the Mystery of the Sun’s Superhot Atmosphere Search News Archive New Theory Might Explain Coronal Heating The Sun’s outer atmosphere, called the corona, is a plasma (highly ionized gas) that is easily seen with the naked eye during a total eclipse. This view of the corona’s delicate structure was photographed by Edwin L. Aguirre during the July 11, 2010, total solar eclipse, which he observed from the South Pacific, on Tatakoto Atoll in French Polynesia’s Tuamotu Archipelago. 03/23/2012 By Edwin L. Aguirre The Sun, whose light and heat has made life possible here on Earth, has been studied in great detail since the invention of the telescope in the 17th century. Yet fundamental questions remain about the nature of this star nearest to our home planet.

One of them is the problem of the heating of the Sun’s tenuous outer atmosphere, known as the corona , which is composed of charged particles and extends millions of miles into interplanetary space. In the late 1930s and early '40s, scientists discovered that the corona is extremely hot — some 2 million degrees. And yet the Sun’s visible surface, called the photosphere, is a “mere” 6,000 degrees. So how can the photosphere heat the surrounding corona to such incredibly high temperatures? “This has been a longstanding problem in solar physics and astrophysics,” says Prof. Paul Song of the Physics and Applied Physics Department. “If the photosphere is indeed responsible for heating the corona, then it contradicts the second law of thermodynamics, which states that heat flows from higher-temperature regions to lower ones, and not vice versa.” Song, who directs UMass Lowell’s Center for Atmospheric Research (CAR), says what makes the problem worse is that another observation shows that a large amount of energy actually radiates from the lower part of the solar atmosphere, a region known as the chromosphere.

“This means the energy from the Sun has to not only heat the corona but also provide energy for chromospheric radiation,” he says. “Quantitatively, the energy loss in radiation is a factor of 100 bigger than what is needed to heat the atmosphere to 2 million degrees!” Song and CAR Distinguished Research Professor Vytenis Vasyliunas proposed a new theory that might help explain this apparent anomaly and lead to the final resolution of the coronal heating problem. Their findings were published last year in the “ Journal of Geophysical Research .” Like Atomic Bombs Going Off Everywhere “Many people realize the Sun is very turbulent and the energy associated with that turbulence — similar to many atomic bombs going off everywhere on the Sun — can provide the required heat energy,” notes Song. “However, the question is how motional energy can be converted to thermal energy. Previous theories are able to come up with only about a few percent of the required thermal energy based on the observed turbulence energy.” In their paper, Song and Vasyliunas analyzed the perturbation (disturbance) of Alfvén waves as they propagate from the solar surface to the corona through the chromosphere, a rather difficult and complex mathematical-physical task.

Alfvén waves are low-frequency traveling oscillation of the charged particles and the Sun’s magnetic field. Song and Vasyliunas found that the waves’ perturbations are heavily damped, and that the motional energy of the perturbation can be converted to heat in regions where the magnetic field is weaker. The damping and heating is much less in regions of stronger magnetic field, they say. “Conventional wisdom has been to focus on regions of stronger magnetic field because these are where stronger perturbations are observed,” explains Song. “Now everything becomes clear: stronger perturbations are observed in stronger field regions because they are not damped, and vice versa. Our theory is thus able to convert the observed level of turbulence energy to the required thermal energy. We are continuing work on the details and other consequences of the heating mechanism to explain other observed solar phenomena.” He says since coronal heating is essential to understanding the formation of the corona and solar winds, which are the cause of all space-weather phenomena, the new theory will substantially improve our current knowledge about solar storms and space weather. What is solar wind? Is there energy in space? What is solar wind?

The solar wind is a stream of energized, charged particles, primarily electrons and protons, flowing outward from the Sun, through the solar system at speeds as high as 900 km/s and at a temperature of 1 million degrees (Celsius). It is made of plasma. The Sun's corona, taken by the SOHO satellite with a special camera that blocks out light from the Sun's main disk. Courtesy of SOHO consortium. SOHO is a project of international cooperation between ESA and NASA." The solar wind is caused by the hot solar corona, which is the outermost layer of the solar atmosphere, expanding into space. The corona is the "rim" of the Sun that is visible to the naked eye during a solar eclipse. The solar wind is what blows the tails of comets back away from the bodies of comets as they go through the solar system. Comet Hale-Bopp. Photo Credit: A. Dimai and D. Ghirardo, (Col Druscie Obs.), AAC Visible Light - Mission:Science Visible Light National Aeronautics and Space Administration, Science Mission Directorate. (2010). Visible Light. Retrieved , from Mission:Science website: Science Mission Directorate.

"Visible Light" Mission:Science. 2010. National Aeronautics and Space Administration. WAVELENGTHS OF VISIBLE LIGHT All electromagnetic radiation is light, but we can only see a small portion of this radiation—the portion we call visible light. Cone-shaped cells in our eyes act as receivers tuned to the wavelengths in this narrow band of the spectrum. Other portions of the spectrum have wavelengths too large or too small and energetic for the biological limitations of our perception. As the full spectrum of visible light travels through a prism, the wavelengths separate into the colors of the rainbow because each color is a different wavelength. Violet has the shortest wavelength, at around 380 nanometers, and red has the longest wavelength, at around 700 nanometers. Isaac Newton's experiment in 1665 showed that a prism bends visible light and that each color refracts at a slightly different angle depending on the wavelength of the color. Credit: Troy Benesch Each color in a rainbow corresponds to a different wavelength of electromagnetic spectrum. THE SUN'S CORONA The Sun is the dominant source for visible-light waves our eyes receive. The outer-most layer of the Sun's atmosphere, the corona, can be seen in visible light.

But it is so faint it cannot not be seen except during a total solar eclipse because the bright photosphere overwhelms it. The photograph below was taken during a total eclipse of the Sun where the photosphere and chromosphere are almost completely blocked by the moon. The tapered patterns—coronal streamers—around the Sun are formed by the outward flow of plasma that is shaped by magnetic field lines extending millions of miles into space. Credit: © 2008 Miloslav Druckmüller, Martin Dietzel, Peter Aniol, Vojtech Rušin COLOR AND TEMPERATURE As objects grow hotter, they radiate energy dominated by shorter wavelengths, changing color before our eyes. A flame on a blow torch shifts from reddish to bluish in color as it is adjusted to burn hotter. In the same way, the color of stars tells scientists about their temperature. Our Sun produces more yellow light than any other color because its surface temperature is 5,500°C. If the Sun's surface were cooler—say 3,000°C—it would look reddish, like the star Betelgeuse.

If the Sun were hotter—say, 12,000°C—it would look blue, like the star Rigel. Isaac Newton's experiment in 1665 showed that a prism bends visible light and that each color refracts at a slightly different angle depending on the wavelength of the color. Credit: Jenny Mottar; Image Courtesy of SOHO/consortium. The High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter (MRO) captured this spectacular visible light image of Victoria Crater. Credit: NASA/JPL/University of Arizona SPECTRA AND SPECTRAL SIGNATURES Close examination of the visible-light spectrum from our Sun and other stars reveals a pattern of dark lines—called absorption lines. These patterns can provide important scientific clues that reveal hidden properties of objects throughout the universe. Certain elements in the Sun's atmosphere absorb certain colors of light. These patterns of lines within spectra act like fingerprints for atoms and molecules. Looking at the Sun's spectrum, for example, the fingerprints for elements are clear to those knowledgeable about those patterns. Patterns are also evident in a graph of an object's reflectance. Elements, molecules, and even cell structures have unique signatures of reflectance.

A graph of an object's reflectance across a spectrum is called a spectral signature. Spectral signatures of different Earth features within the visible light spectrum ARE shown below. Credit: Jeannie Allen ACTIVE REMOTE SENSING—ALTIMETRY Laser altimetry is an example of active remote sensing using visible light. NASA's Geoscience Laser Altimeter System (GLAS) instrument onboard the Ice, Cloud, and land Elevation Satellite (ICESat) enabled scientists to calculate the elevation of Earth's polar ice sheets using lasers and ancillary data. Changes in elevation over time help to estimate variations in the amount of water stored as ice on our planet. The image below shows elevation data over the West Antarctic Ice Streams. Laser altimeters can also make unique measurements of the heights and characteristics of clouds, as well as the top and structure of the vegetation canopy of forests. They can also sense the distribution of aerosols from sources such as dust storms and forest fires. Credit: NASA/Goddard Space Flight Center Solar Eclipse: What is a Total Solar Eclipse & When is the Next One?

See photos of the 2016 total solar eclipse The next one will be an annular solar eclipse (also known as a "ring of fire" solar eclipse) on Sept. 1, 2016. The total solar eclipse of 2016 reaches totality in this still image from a NASA webcast on March 8, 2016 from Woleai Island in Micronesia, where it was March 9 local time during the eclipse. Credit: NASA TV A solar eclipse occurs when the moon gets between Earth and the sun, and the moon casts a shadow over Earth. A solar eclipse can only take place at the phase of new moon, when the moon passes directly between the sun and Earth and its shadows fall upon Earth’s surface. But whether the alignment produces a total solar eclipse, a partial solar eclipse or an annular solar eclipse depends on several factors, all explained below. The fact that an eclipse can occur at all is a fluke of celestial mechanics and time. Since the moon formed about 4.5 billion years ago , it has been gradually moving away from Earth (by about 1.6 inches, or 4 centimeters per year).

Right now the moon is at the perfect distance to appear in our sky exactly the same size as the sun, and therefore block it out. But this is not always true. When is the next solar eclipse? The next solar eclipse visible from North America will be a total eclipse on Aug. 21, 2017. It will sweep across the continental United States from Oregon to Georgia. How Solar Eclipses Work: When the moon covers up the sun, skywatchers delight in the opportunity to see a rare spectacle. See how solar eclipses occur in this Space.com infographic . Credit: Karl Tate, SPACE.com Contributor Types of solar eclipses There are four types of solar eclipses: total, annular, partial and hybrid. Here’s what causes each type: Total solar eclipses These are a happy accident of nature. The sun's 864,000-mile diameter is fully 400 times greater than that of our puny moon , which measures just about 2,160 miles.

But the moon also happens to be about 400 times closer to Earth than the sun (the ratio varies as both orbits are elliptical), and as a result, when the orbital planes intersect and the distances align favorably, the new moon can appear to completely blot out the disk of the sun. On the average a total eclipse occurs somewhere on Earth about every 18 months. There are actually two types of shadows: the umbra is that part of the shadow where all sunlight is blocked out. The umbra takes the shape of a dark, slender cone. It is surrounded by the penumbra, a lighter, funnel-shaped shadow from which sunlight is partially obscured. During a total solar eclipse, the moon casts its umbra upon Earth's surface; that shadow can sweep a third of the way around the planet in just a few hours. Those who are fortunate enough to be positioned in the direct path of the umbra will see the sun's disk diminish into a crescent as the moon's dark shadow rushes toward them across the landscape. During the brief period of totality, when the sun is completely covered, the beautiful corona — the tenuous outer atmosphere of the sun — is revealed.

Totality may last as long as 7 minutes 31 seconds, though most total eclipses are usually much shorter. On Jan. 4, 2011, the moon passed in front of the sun in a partial solar eclipse - as seen from parts of Earth. Here, the joint Japanese-American Hinode satellite captured the same breathtaking event from space. The unique view created what's called an annular solar eclipse. Credit: Hinode/XRT Partial solar eclipses A partial solar eclipse occurs when only the penumbra (the partial shadow) passes over you. In these cases, a part of the sun always remains in view during the eclipse. How much of the sun remains in view depends on the specific circumstances. Usually the penumbra gives just a glancing blow to our planet over the polar regions; in such cases, places far away from the poles but still within the zone of the penumbra might not see much more than a small scallop of the sun hidden by the moon. In a different scenario, those who are positioned within a couple of thousand miles of the path of a total eclipse will see a partial eclipse. The closer you are to the path of totality, the greater the solar obscuration.

If, for instance, you are positioned just outside of the path of the total eclipse, you will see the sun wane to a narrow crescent, then thicken up again as the shadow passes by. Annular solar eclipses An annular eclipse, though a rare and amazing sight, is far different from a total one. The sky will darken ... somewhat; a sort of weird “counterfeit twilight” since so much of the sun still shows. The annular eclipse is a subspecies of a partial eclipse, not total. The maximum duration for an annular eclipse is 12 minutes 30 seconds. However, an annular solar eclipse is similar to a total eclipse in that the moon appears to pass centrally across the sun. The difference is, the moon is too small to cover the disk of the sun completely. Because the moon circles Earth in an elliptical orbit, its distance from Earth can vary from 221,457 miles to 252,712 miles. But the dark shadow cone of the moon’s umbra can extend out for no longer than 235,700 miles; that’s less than the moon’s average distance from Earth .

So if the moon is at some greater distance, the tip of the umbra does not reach Earth. During such an eclipse, the antumbra, a theoretical continuation of the umbra, reaches the ground, and anyone situated within it can look up past either side of the umbra and see an annulus, or “ring of fire” around the moon. A good analogy is putting a penny atop a nickel, the penny being the moon, the nickel being the sun. Hybrid solar eclipses These are also called annular-total (“A-T”) eclipses. This special type of eclipse occurs when the moon’s distance is near its limit for the umbra to reach Earth. In most cases, an A-T eclipse starts as an annular eclipse because the tip of the umbra falls just short of making contact with Earth; then it becomes total, because the roundness of the planet reaches up and intercepts the shadow tip near the middle of the path, then finally it returns to annular toward the end of the path. Because the moon appears to pass directly in front of the sun, total, annular and hybrid eclipses are also called “central” eclipses to distinguish them from eclipses that are merely partial.

Of all solar eclipses, about 28 percent are total; 35 percent are partial; 32 percent annular; and just 5 percent are hybrids. Predictions of solar eclipses Eclipses do not happen at every new moon, of course. This is because the moon’s orbit is tilted just over 5 degrees relative to Earth’s orbit around the sun. For this reason, the moon’s shadow usually passes either above or below Earth, so a solar eclipse doesn’t occur. But as a rule, at least twice each year (and sometimes as many as five times in a year), a new moon will align itself in just such a way to eclipse the sun. That alignment point is called a node. Depending on how closely the new moon approaches a node will determine whether a particular eclipse is central or partial. And of course, the moon’s distance from the Earth — and to a lesser degree, Earth’s distance from the sun — will ultimately determine whether a central eclipse is total, annular or a hybrid. And these alignments don’t happen haphazardly, for after a specific interval of time, an eclipse will repeat itself or return.

This interval is known as the Saros cycle and was known as far back as the days of the early Chaldean astronomers some 28 centuries ago. The word Saros means “repetition” and is equal to 18 years, 11⅓ days (or a day less or more depending on the number of leap years that have intervened). After this interval, the relative positions of the sun and moon relative to a node are nearly the same as before. That third of a day in the interval causes the path of each eclipse of a series to be displaced in longitude a third of the way around Earth to the west with respect to its predecessor. For example, on March 29, 2006, a total eclipse swept across parts of western and northern Africa and then across southern Asia. One Saros later, on April 8, 2024, this eclipse will recur, except instead of Africa and Asia, it will track across northern Mexico, the central and eastern United States and the Maritime provinces of Canada. Solar eclipse safety You should never look directly at the sun, but there are ways to safely observe an eclipse. See how to safely observe a solar eclipse with this Space.com infographic .

Credit: Karl Tate, SPACE.com Contributor As a solar eclipse approaches, the mainstream media often will provide a variety of warnings and advisories against looking at the sun with bare eyes, as blindness could ensue. This has given most people the idea that eclipses are dangerous. Not so! It’s the sun that is dangerous — all the time! The sun constantly emits invisible infrared rays that can damage your eyes. Ordinarily, we have no reason to gaze at the sun. An eclipse gives us a reason, but we shouldn’t. There are safe ways, however . . . By far, the safest way to view a solar eclipse is to construct a “pinhole camera.” A pinhole or small opening is used to form an image of the sun on a screen placed about 3 feet (or about 1 meter) behind the opening. Binoculars or a small telescope mounted on a tripod can also be used to project a magnified image of the sun onto a white card. The farther away the card, the larger you can focus the image. Look for sunspots. Notice that the sun appears somewhat darker around its limb or edge.

This method of solar viewing is safe so long as you remember not to look through the binoculars or telescope when they are pointed toward the sun; put another way, never look directly at the sun when any part of its blindingly bright surface is visible. A variation on the pinhole theme is the “pinhole mirror.” Cover a pocket-mirror with a piece of paper that has a ¼-inch hole punched in it. Open a sun-facing window and place the covered mirror on the sunlit sill so it reflects a disk of light onto the far wall inside. The disk of light is an image of the sun’s face. The farther away from the wall is the better; the image will be only 1 inch across for every 9 feet (or 3 centimeters for every 3 meters) from the mirror. Modeling clay works well to hold the mirror in place. Experiment with different-sized holes in the paper. Again, a large hole makes the image bright, but fuzzy, and a small one makes it dim but sharp. Darken the room as much as possible. Be sure to try this out beforehand to make sure the mirror’s optical quality is good enough to project a clean, round image.

Of course, don’t let anyone look at the sun in the mirror. If you’re around leafy trees, look at the shadow cast by them during the partial phases. What do you see? Is it worth a photograph? You will see scores of partially eclipsed suns projected through pinhole gaps between the leaves. This is caused by diffraction, a property of light. According to Vince Huegele, an optical physicist at the NASA Marshall Space Flight Center, the light rays do not shoot straight by the rim of the gaps, or a pinhole, but bend around the edge. This wave effect creates a pattern of rings that resembles a bull's eye. Acceptable filters for unaided visual solar observations include aluminized Mylar. Some astronomy dealers carry Mylar filter material specially designed for solar observing. Also acceptable is shade 14 arc-welder’s glass, available for just a few dollars at welding supply shops. Of course, it is always a good idea to test your filters and/or observing techniques before eclipse day. Unacceptable filters include sunglasses, old color film negatives, black-and-white film that contains no silver, photographic neutral-density filters and polarizing filters.

Although these materials have very low visible-light transmittance levels, they transmit an unacceptably high level of near-infrared radiation that can cause a thermal retinal burn. The fact that the sun appears dim, or that you feel no discomfort when looking at the sun through these types of filters, is no guarantee that your eyes are safe. There is one time when you can safely look directly at the sun: during a total eclipse, when the sun's disk is entirely covered. During those few precious seconds or minutes, the magnificent corona shines forth in all its glory surrounding the darkened sun; a marvelous fringe of pearly white light. It differs in size, in tints and patterns from eclipse to eclipse. It is always faint and delicate, with a sheen like a pale aurora. It has a variable appearance. Sometimes it has a soft continuous look; at other times, long rays of it shoot out in three or four directions. It may stand out from the disk in filmy petals and streamers. But when the sun begins to again emerge into view, the corona quickly disappears and you’ll need to protect your eyes once again. This photo of the partial solar eclipse of Sept.

13, 2015, was snapped by astrophotographer K.J. Mulder from his home in South Africa. Credit: K.J. Mulder/ Worlds in Ink Eclipses in ancient history As best as we can determine, the earliest record of a solar eclipse occurred over four millennia ago. In China, it was believed that the gradual blotting out of the sun was caused by a dragon who was attempting to devour the sun, and it was the duty of the court astronomers to shoot arrows, beat drums and raise whatever cacophony they could to frighten the dragon away. In the ancient Chinese classic Shujing (or Book of Documents) is the account of Hsi and Ho, two court astronomers who were caught completely unaware by a solar eclipse, having gotten drunk just before the event began. In the aftermath, Zhong Kang, the fourth emperor of the Xia dynasty ordered that Hsi and Ho be punished by having their heads chopped off. The eclipse in question was that of Oct. 22 in the year 2134 B.C.

In the Bible, in the book of Amos 8:9, are the words, “I will cause the sun to go down at noon, and I will darken the Earth in the clear day.” Biblical scholars believe this is a reference to a celebrated eclipse observed at Nineveh in ancient Assyria on June 15, 763 B.C. An Assyrian tablet also attests to the event. A solar eclipse even stopped a war. According to the historian Herodotus, there was a five-year war that raged between the Lydians and the Medes. As the war was about to move into its sixth year, a Greek sage, Thales of Miletus foretold to the Ionians that the time was soon approaching when day would turn to night. On May 17, 603 B.C. the sun faded away just as Thales had alluded that it would.

So believing that it was a sign from above, the combatants called a truce, which was cemented by a double marriage, for, as Herodotus wrote: “Without some strong bond, there is little of security to be found in men’s covenants.” And giving new meaning to the term, “Scared to death,” is the timid emperor Louis of Bavaria, the son of Charlemagne, who witnessed an unusually long total eclipse of the sun on May 5, A.D. 840, which lasted for over five minutes. But no sooner had the sun begun to emerge back into view, Louis was so overwhelmed by what he had just seen that he died of fright! Modern study of eclipses Astronomers have learned much by studying eclipses and by the 18th century, observations of solar eclipses were recognized as providing veritable treasure troves of astronomical information, though sometimes getting that information wasn’t easy. Samuel Williams, a professor at Harvard, led an expedition to Penobscot Bay, Maine, to observe the total solar eclipse of Oct. 27, 1780.

As it turned out, this eclipse took place during the Revolutionary War, and Penobscot Bay lay behind enemy lines. Fortunately, the British granted the expedition safe passage, citing the interest of science above political differences. And yet in the end, it was all for naught. Williams apparently made a crucial error in his computations and inadvertently positioned his men at Islesboro — just outside the path of totality — likely finding this out with a heavy heart when the narrowing crescent of sunlight slid completely around the dark edge of the moon and then started to thicken! During a total solar eclipse, a few ruby-red spots may seem to hover around the jet-black disk of the moon. Those are solar prominences, tongues of incandescent hydrogen gas rising above the surface of the sun. During the total eclipse of Aug. 18, 1868, the French astronomer Pierre Janssen trained his spectroscope on the prominences and discovered a new chemical element. Two English astronomers, J. Norman Lockyer and Edward Frankland, later named it “ helium ,” from the Greek helios (the sun). The gas was not identified on Earth until 1895.

And because sunlight is blocked during a total eclipse, some of the brighter stars and planets can be observed in the darkened sky. Under such conditions astronomers were able to test part of Einstein’s now-celebrated general theory of relativity . That theory predicted that light from stars beyond the sun would bend from a straight path in a certain way as it passed the sun. The positions of stars photographed near the sun’s edge during a total eclipse on May 29, 1919, were compared with photographs of the same region of the sky taken at night; the results strongly supported Einstein’s theory. Our modern technology now allows astronomers to make most of the observations that once had to await an eclipse. But a total eclipse of the sun will always remain among the most impressive of natural spectacles and is a sight that will always be remembered. Be sure to put it on your bucket list; you will not be disappointed. Additional resources What is the Chromosphere? What is the Chromosphere?

Last Modified Date: 21 December 2016 Copyright Protected: Adorable animal families that will make you "aww" The chromosphere is the second outermost most layer of the sun’s atmosphere, which is only visible to the naked eye during a solar eclipse . The chromosphere is notable for being hotter than the photosphere , the next layer towards the sun. The chromosphere is located between the photosphere and the corona, which is the outermost part of the sun’s atmosphere. The chromosphere is around 1,250 miles (2,011 kilometers) deep. Its name, which means color sphere, comes from the fact that it is a reddish color. This is caused a particular type of hydrogen. Despite this color, it is usually impossible to see the chromosphere from Earth without special equipment. The one exception is during a total solar eclipse, when the moon is directly in line between the earth and the sun. At this point, the chromosphere appears as a series of red blotches around a solid black circle. Logic would suggest that the chromosphere would be cooler than other parts of the sun’s atmosphere because it is the furthest away.

In reality, it is considerably hotter, and appears to get hotter further away from the sun. The next nearest layer, the photosphere, is around 7,250 degrees Fahrenheit (4,010 degrees Celsius), while parts of the chromosphere are almost 36,000 degrees Fahrenheit (19,982 degrees Celsius). One theory for this apparent disparity is that it contains magnetic fields projected outwards from the photosphere. Electric currents flow through these fields from the photosphere to the corona. This process can lose some energy in the fields, which produces the higher temperature. It’s thought the energy may be lost through magnet field lines being disturbed and having to oscillate in an attempt to return to their original form. When visible, the chromosphere appears to flow. This is because gases are emitted from it at varying wavelengths. During an eclipse in 1868, astronomers noted a bright yellow line in the chromosphere. At first they thought it was sodium, but the wavelength showed it must be a previously uncharted element. They named it helium, after the Greek name for the sun, Helios. It wasn’t until 1895 that scientists could isolate helium on Earth.

There is a considerable amount of movement of gases within the chromosphere. The most common are spicules , vertical plumes of gas which rise away from and then back towards the sun. Their counterparts are fibrils, which travel horizontally and last for around 20 minutes, twice as long as spicules. The chromosphere can also produce filaments, which are made up of plasma which is cooler than the surrounding gases and thus easier to see. These can sometimes lead to coronal mass ejections, where plasma leaves the sun’s atmosphere completely. This can affect the solar system’s equivalent of a planet’s weather and may even have an effect on spacecraft and other satellites. Ad

Question: What is the name of the outer plasma atmosphere of the sun, visible with the naked eye during an eclipse?
Answer: Corona