Solar eclipse

Photo taken during the French 1999 eclipse

A solar eclipse occurs when the Moon passes in front of the Sun and obscures it totally or partially. This configuration can only occur at New Moon, when the Sun and Moon are in conjunction, as seen from Earth. A total solar eclipse is considered by many to be the most spectacular natural phenomenon that one can observe.

Types of solar eclipses

There are four types of solar eclipses:

  • A total eclipse occurs when the Sun is completely obscured by the Moon. The intensely bright disk of the Sun is replaced by the dark outline of the Moon, and the much fainter corona is visible (see image right). During any one eclipse, a total eclipse is visible only from a fairly narrow track on the surface of the Earth.
  • An annular eclipse occurs when the Sun and Moon are exactly in line, but the apparent size of the Moon is smaller than that of the Sun. Hence the Sun appears as a very bright ring surrounding the outline of the Moon.
  • A hybrid eclipse is intermediate between a total and annular eclipse. At some points on the Earth it is visible as a total eclipse; whereas at others it is annular. The generic term for a total, annular or hybrid eclipse is a central eclipse.
  • A partial eclipse occurs when the Sun and Moon are not exactly in line, and the Moon only partially obscures the Sun. This phenomenon can usually be seen from a large part of the Earth outside of the track of a central eclipse. However, some eclipses can only be seen as a partial eclipse, because the central line never intersects the Earth's surface.

The reason why some solar eclipses are total and others are annular has to do with the elliptical nature of the Moon's orbit around Earth. One of the most remarkable co-incidences in nature is that (i) the Sun lies about 400 times as far from Earth as does the Moon, and (ii) the Sun is also about 400 times the diameter of the Moon. As seen from Earth, therefore, the Sun and the Moon appear to be about the same size in the sky - about 1/2 of a degree in angular measure. Because the Moon's orbit around Earth is an ellipse rather than a circle, however, at some times during the month the Moon is further away, and at other times it is closer to Earth, than average. The furthest point in the orbit is referred to as apogee, and the closest point is called perigee.

When a solar eclipse occurs when the Moon is at or near perigee, it appears large enough to cover the bright disk, or photosphere, of the Sun completely, and a total eclipse occurs. When a solar eclipse occurs when the Moon is at or near apogee, however, it appears smaller, and it cannot cover the Sun completely. In that case, at the time of greatest eclipse there remains a thin annulus (or ring) of brilliant Sun left uncovered. Hence the term annular eclipse. Slightly more annular eclipses than total eclipses occur, because on average the Moon lies too far away from Earth to cover the Sun completely.

Terminology

The term eclipse is actually a misnomer: The phenomenon of the Moon passing in front of the Sun is actually an occultation. Properly speaking, an eclipse occurs when one object passes into the shadow cast by another object. When the Moon disappears at Full Moon by passing into Earth's shadow, the event is properly called an eclipse, but when the Moon passes in front of the Sun, we see an occultation of the Sun by the Moon.

Photo taken by Wikipedia editor Luc Viatour (Lviatour) during the French 1999 eclipse Photo taken during the Spanish 2005 annular eclipse Photo taken in Valladolid (Spain) during the October 3, 2005 annular eclipse People observing a Solar eclipse in Iceland 2002

Observing a solar eclipse

Looking directly at the photosphere of the Sun (the bright disk of the Sun itself), even for just a few seconds, can cause permanent damage to the retina of the eye, because of the intense visible and invisible radiation that the photosphere emits. This damage can result in permanent impairment of vision, up to and including blindness. The retina has no sensitivity to pain, and the effects of retinal damage may not appear for hours, so there is no warning that injury is occurring.

Under normal conditions, the Sun is so bright that it's difficult to stare at it directly, so there is no tendency to look at it in a way that might damage the eye. However, during an eclipse, with so much of the Sun covered, it is easier and more tempting to stare at it. Unfortunately, looking at the Sun during an eclipse is just as dangerous as looking at it outside an eclipse, except during the brief period of totality, when the Sun's disk is completely covered (totality occurs only during a total eclipse and only very briefly—it does not occur during a partial or annular eclipse). Viewing the Sun's disk through any kind of optical aid (binoculars, a telescope, or even an optical camera viewfinder) is even more hazardous, although just viewing it with the naked eye can easily cause damage.

Viewing partial and annular eclipses

Viewing the Sun during partial and annular eclipses (and during total eclipses outside the brief period of totality) requires special eye protection, or indirect viewing methods.

The Sun's disk can be viewed using appropriate filtration to block the harmful part of the Sun's radiation. Sunglasses are not safe, since they do not block the harmful and invisible infrared radiation which causes retinal damage. Only properly designed and certified solar filters should ever be used for direct viewing of the Sun's disk.

The safest way to view the Sun's disk is by indirect projection. This can be done by projecting an image of the disk onto a white piece of paper or card using a pair of binoculars (with one of the lenses covered), a telescope, or another piece of cardboard with a small hole in it (about 1 mm diameter), often called a pinhole camera. The projected image of the Sun can then be safely viewed; this technique can be used to observe sunspots, as well as eclipses. However, care must be taken to ensure that no one looks through the projector (telescope, pinhole, etc.) directly.

Viewing the Sun's disk on a video display screen (provided by a video camera or digital camera) is safe, although the camera itself may be damaged by direct exposure to the Sun. The optical viewfinders provided with some video and digital cameras are not safe.

These precautions apply to viewing the Sun at any time except during the totality phase of a total solar eclipse (see below).

Viewing totality during total eclipses

Contrary to popular belief, it is safe to observe the total phase of a total solar eclipse directly with the unaided eye, binoculars or a telescope, when the Sun's photosphere is completely covered by the Moon; indeed, this is a very spectacular and beautiful sight, and it is too dim to be seen through filters. The Sun's faint corona will be visible, and even the chromosphere, solar prominences, and possibly even a solar flare may be seen. However, it is important to stop directly viewing the Sun promptly at the end of totality. The exact time and duration of totality for the location from which the eclipse is being observed should be determined from a reliable source (local astronomers, etc.). Note that it is never safe to look at an annular or partial eclipse directly, because the Sun's disk is never completely covered during this type of eclipse.

Additional information

For more information on safe eclipse viewing, see:

  • Eye Safety During Solar Eclipses, Fred Espenak, NASA Goddard Space Flight Center
  • How to Watch a Partial Solar Eclipse Safely, Alan M. MacRobert, Sky & Telescope magazine

Eclipse Predictions

Geometry of an Eclipse

Diagram of solar eclipse (not to scale)

The diagram to the right shows the alignment of the Sun, Moon and Earth at a solar eclipse. The dark gray region to the right of the moon is the umbra, where the Sun is completely obscured by the Moon. The small area where the umbra touches the Earth's surface is where a total eclipse will be seen. The larger light gray area is the penumbra, in which a partial eclipse will be seen.

Motion of the Moon and Earth

The Moon's orbit around the Earth is inclined at an angle of just over 5 degrees to the plane of the Earth's orbit around the Sun (the ecliptic). Because of this, at the time of a New Moon, the Moon will usually pass above or below the Sun. A solar eclipse can occur only when the New Moon occurs close to one of the points (known as nodes) where the Moon's orbit crosses the ecliptic – hence the name.

The Moon's orbit is also elliptical, which means that the distance of the Moon from the Earth can vary by about 6% from its average value. This means that the apparent size of the Moon is sometimes larger or smaller than average, and it is this effect that leads to the difference between total and annular eclipses (the distance of the Earth from the Sun also varies during the year, but this is a smaller effect). On average, the Moon appears to be slightly smaller than the Sun, so the majority (about 60%) of central eclipses are annular. It is only when the Moon is closer to the Earth than average (near its perigee) that a total eclipse occurs.

The Moon orbits the Earth in approximately 27.3 days, relative to a fixed frame of reference. This is known as the sidereal month. However, during one sidereal month, the Earth has moved on in its orbit around the Sun. This means that the average time between one New Moon and the next is longer, and is approximately 29.6 days. This is known as the synodic month, and corresponds to what is commonly called the lunar month.

The Moon crosses from south to north of the ecliptic at its ascending node. However, the nodes of the Moon's orbit are gradually moving in a retrograde motion, due the the action of the Sun's gravity on the Moon's motion, and they make a complete circuit every 18.5 years. This means that the time between each passage of the Moon through the ascending node is slightly shorter than the sidereal month. This period is called the draconitic month.

Finally, the Moon's perigee is moving forwards in its orbit, and makes a complete circuit in about 9 years. The time between one perigee and the next is known as the anomalistic month.

Frequency of Solar Eclipses

The Moon's orbit intersects with the ecliptic at the two nodes that are 180 degrees apart. Therefore, the New Moon occurs close to the nodes at two periods of the year approximately six months apart, and there will always be at least one solar eclipse during these periods. Sometimes the New Moon occurs close enough to a node during two consecutive months. This means that in any given year, there will always be at least two solar eclipses, and there can be as many as five. However, some are visible only as partial eclipses, because the umbra passes either above or below the earth, and others are central only in remote regions of the arctic or antarctic.

Path of an Eclipse

During a central eclipse, the Moon's umbra (or antumbra, in the case of an annular eclipse) moves rapidly from west to east across the Earth. The Earth is also rotating from west to east, but the umbra always moves faster than any given point on the Earth's surface, so it almost always appears to move in a roughly west-east direction across a map of the Earth (there are some rare exceptions to this which can occur during an eclipse of the midnight sun in arctic or antarctic regions).

The width of the track of a central eclipse varies according to the relative apparent diameters of the Sun and Moon. In the most favourable circumstances, when a total eclipse occurs very close to perigee, the track can be over 250 km wide and the duration of totality may be over 7 minutes. Outside of the central track, a partial eclipse can usually be seen over a much larger area of the Earth.

Occurrence of Eclipses at a given place

Total Solar Eclipse Paths: 1001-2000. This image was merged from 50 separated images from http://sunearth.gsfc.nasa.gov/eclipse/

Total solar eclipses are rare events. Although they occur somewhere on Earth approximately every 18 months, it has been estimated that they recur at any given place only once every 370 years, on average (Stephenson, p.54). Then, after waiting so long, the total eclipse only lasts for a few minutes, as the Moon's umbra moves eastward at over 1700 km/h. Totality can never last more than 7 min 40 s, and is usually much shorter. During each millennium there are typically fewer than 10 total solar eclipses exceeding 7 minutes. The last time this happened was June 30, 1973. Observers aboard a Concorde aircraft were able to stretch totality to about 74 minutes by flying along the path of the Moon's umbra. The next eclipse of comparable duration will not occur until June 25, 2150. The longest total solar eclipse during the 8,000-year period from 3000 BC to 5000 AD will occur on July 16, 2186, when totality will last 7 min 29 s. (eclipse predictions by Fred Espenak, NASA/GSFC.)

For astronomers, a total solar eclipse forms a rare opportunity to observe the corona (the outer layer of the Sun's atmosphere). Normally this is not visible because the photosphere is much brighter than the corona.

Eclipse Cycles

If the date and time of a solar eclipse is known, it is possible to predict other eclipses using eclipse cycles. Two such cycles are the Saros and the Inex. The Saros cycle is probably the most well known, and one of the best, eclipse cycles. The Inex cycle is itself a poor cycle, but it is very convenient in the classification of eclipse cycles. After a Saros cycle finishes, a new Saros cycle begins 1 Inex later (hence its name: in-ex).

Historical solar eclipses

A solar eclipse of 15 June 763 BC mentioned in an Assyrian text is important for the Chronology of the Ancient Orient. This is the earliest solar eclipse that can be exactly dated. There have been other claims to date earlier eclipses, in Babylon and also in China, but these are highly disputed and rely on much supposition. For a discussion, see the text by Stephenson.

Herodotus wrote that Thales of Milete predicted an eclipse which occurred during a war between the Medians and the Lydians. Soldiers on both sides put down their weapons and declared peace as a result of the eclipse. Exactly which eclipse was involved has remained uncertain, although the issue has been studied by hundreds of ancient and modern authorities. One likely candidate took place on May 28, 585 BC, probably near the Halys river in the middle of modern Turkey.

An annular eclipse of the Sun occurred at Sardis on February 17, 478 BC, while Xerxes was departing for his expedition against Greece, as Herodotus, VII, 37 recorded ([Hind and Chambers, 1889: 323] considered this absolute date more than a century ago). Herodotus (book IX, 10, book VIII, 131, and book IX, 1) reports that another solar eclipse was observed in Sparta during the next year, on August 1, 477 BC. The sky suddenly darkened in the middle of the sky, well after the battles of Thermopylae and Salamis, after the departure of Mardonius to Thessaly at the beginning of the spring of (477 BC) and his second attack on Athens, after the return of Cleombrotus to Sparta. Note that the modern conventional dates are different by a year or two, and that these two eclipse records have been ignored so far.

Other Observations

During a solar eclipse special observations can be done with the unaided eye. Normally the spots of light which fall through the small openings between the leaves of a tree, have a circular shape. These are images of the sun. During a partial eclipse, the light spots will show the partial shape of the sun, as seen on the picture.

Images of the sun during a partial eclipse through the leaves of a tree

Special observation campaigns

  • May 30, 1965: Launch of rockets at Charlestown, USA
  • May 20, 1966: Launch of rockets at Karystos, Greece to watch the solar eclipse
  • November 12, 1966: Launch of two Titus-rockets fom Las Palmas, Argentina
  • February 26, 1979: Launch of rockets from Red Lake, Canada
  • February 16, 1980: Launch of rockets from San Marco platform

Solar eclipse before sunrise or after sunset

It is possible for a solar eclipse to attain totality (or in the event of a partial eclipse, near totality) before sunrise or after sunset from a particular location. When this occurs shortly before the former or after the latter, the sky will appear much darker than it would otherwise be immediately before sunrise or after sunset. On these occasions, an object — especially a planet (often Mercury) — may be visible near the sunrise or sunset point of the horizon when it could not have been seen without the eclipse.

Simultaneous occurrence of solar eclipse and transit of a planet

In principle, the simultaneous occurrence of a Solar eclipse and a transit of a planet is possible. But these events are extremely rare because of their short durations. The next anticipated simultaneous occurrence of a Solar eclipse and a transit of Mercury will be on July 5, 6757, and of a Solar eclipse and a transit of Venus is expected on April 5, 15232.

Only 5 hours after the transit of Venus on June 4, 1769 there was a total solar eclipse, which was visible in Northern America, Europe and Northern Asia as partial solar eclipse. This was the lowest time difference between a transit of a planet and a solar eclipse in the historical past.

More common — but still quite rare — is a conjunction of any planet (not confined exclusively to Mercury or Venus) at the time a total solar eclipse, in which event the planet will be visible very near the eclipsed Sun, when without the eclipse it would have been lost in the Sun's glare. At one time, some scientists — including Albert Einstein — hypothesized that there may have been a planet even closer to the Sun than Mercury; the only way to confirm its existence would have been to observe it during a total solar eclipse. When no such planet was found during such an eclipse, the possibility of its existence was ruled out.

Solar eclipses by artificial satellites

Artificial satellites can also get in the line between Earth and Sun. But none are large enough to cause an eclipse. At the altitude of the International Space Station, for example, an object would need to be about 3.35 km across to blot the Sun out entirely. This means the best you can get is a satellite transit, but these events are difficult to watch, because the zone of visibility is very small. The satellite passes over the face of the Sun in about a second, typically. Like a transit of a planet it will not get dark. [1]

Past and future eclipses

Although there is a total eclipse visible somewhere on Earth most years, some are more conveniently observed than others. Eclipses where the path of totality crosses major population centres generate the most interest in the general public.

Selected past and upcoming eclipses are:

(*) Duration of central eclipse.


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(*) Duration of central eclipse.. 2005 Billboard Music Awards. Selected past and upcoming eclipses are:. Her favorite sports teams are the Boston Red Sox, Dallas Cowboys, and Los Angeles Lakers. Eclipses where the path of totality crosses major population centres generate the most interest in the general public. She is a big sports fan. Although there is a total eclipse visible somewhere on Earth most years, some are more conveniently observed than others. Carrie Underwood and Drake Clark agreed to break it off since the two were not spending enough time together.

[1]. During American Idol she dated Drake Clark, also from Northeastern State University. Like a transit of a planet it will not get dark. Pictures of the two of them surfaced when Chad Eagelton posted pictures of him and Carrie at the Maxim after party on his Facebook account. The satellite passes over the face of the Sun in about a second, typically. As of November 2005, Carrie Underwood is currently dating Northeastern State University student Chad Eagleton. This means the best you can get is a satellite transit, but these events are difficult to watch, because the zone of visibility is very small. [4].

At the altitude of the International Space Station, for example, an object would need to be about 3.35 km across to blot the Sun out entirely. "Don't Forget to Remember Me" was recently announced as the next single. But none are large enough to cause an eclipse. On January 9th 2006, Some Hearts was certified Double Platinum by the RIAA with shipments of over 2 million units, making it the fastest-selling debut country album in the history of Nielsen SoundScan.[3]. Artificial satellites can also get in the line between Earth and Sun. In December 2005, Underwood was named "Oklahoman of the Year" by Oklahoma Today magazine. When no such planet was found during such an eclipse, the possibility of its existence was ruled out. The large first week sales of Some Hearts made it #1 on the Billboard Top Country Albums chart and the biggest debut of any country artist since the advent of the SoundScan system in 1990.

At one time, some scientists — including Albert Einstein — hypothesized that there may have been a planet even closer to the Sun than Mercury; the only way to confirm its existence would have been to observe it during a total solar eclipse. When the week's sales figures were tabulated, Some Hearts entered the Billboard 200 chart with 315,000 copies sold. More common — but still quite rare — is a conjunction of any planet (not confined exclusively to Mercury or Venus) at the time a total solar eclipse, in which event the planet will be visible very near the eclipsed Sun, when without the eclipse it would have been lost in the Sun's glare. [2] On that same day, she presented an award and performed "Jesus, Take The Wheel" at the 39th Country Music Association awards in New York City. This was the lowest time difference between a transit of a planet and a solar eclipse in the historical past. Her initial album release, entitled Some Hearts, hit store shelves on November 15, 2005. Only 5 hours after the transit of Venus on June 4, 1769 there was a total solar eclipse, which was visible in Northern America, Europe and Northern Asia as partial solar eclipse. The single also debuted at #48 on the Billboard Hot 100 where it currently sits at #26 after reaching a peak at #25.

The next anticipated simultaneous occurrence of a Solar eclipse and a transit of Mercury will be on July 5, 6757, and of a Solar eclipse and a transit of Venus is expected on April 5, 15232. It is currently ranked at #1 in its thirteenth week on that chart. But these events are extremely rare because of their short durations. It received so much airplay that it debuted at #39 on the Billboard Country Chart in its first week, setting a record. In principle, the simultaneous occurrence of a Solar eclipse and a transit of a planet is possible. Underwood's second single, "Jesus, Take The Wheel" was made available for radio airplay on October 18, 2005. On these occasions, an object — especially a planet (often Mercury) — may be visible near the sunrise or sunset point of the horizon when it could not have been seen without the eclipse. Underwood is also the latest spokesperson for Skechers shoes, following in the footsteps of Britney Spears and Christina Aguilera.

When this occurs shortly before the former or after the latter, the sky will appear much darker than it would otherwise be immediately before sunrise or after sunset. The T-Shirts are now available to buy with proofs of purchase. It is possible for a solar eclipse to attain totality (or in the event of a partial eclipse, near totality) before sunrise or after sunset from a particular location. She is also wearing vintage Hershey T-shirts that feature Hershey's, Almond Joy, Kit Kat, Reeses and other chocolate brand logos. During a partial eclipse, the light spots will show the partial shape of the sun, as seen on the picture. The commercials have Underwood singing Hershey jingles like the jingles for Hershey's, Kit Kat and Almond Joy. These are images of the sun. In the same year, she starred in ads for Hershey's Chocolate.

Normally the spots of light which fall through the small openings between the leaves of a tree, have a circular shape. Underwood performed a well-received "The Star Spangled Banner" before Game 4 of the 2005 NBA Finals at the Palace of Auburn Hills in Michigan. During a solar eclipse special observations can be done with the unaided eye. [1] The B-side is "Independence Day", a cover of the Martina McBride hit. Note that the modern conventional dates are different by a year or two, and that these two eclipse records have been ignored so far. Underwood's version was shunned by country radio reaching a peak of #59 on the country charts. The sky suddenly darkened in the middle of the sky, well after the battles of Thermopylae and Salamis, after the departure of Mardonius to Thessaly at the beginning of the spring of (477 BC) and his second attack on Athens, after the return of Cleombrotus to Sparta. The single debuted at #1 on the Billboard Hot 100, with first-week sales of 170,000 copies, and briefly stopped Mariah Carey's run at #1 with "We Belong Together." One week later, runner-up, Bo Bice, released his version of the song, which debuted at #2.

Herodotus (book IX, 10, book VIII, 131, and book IX, 1) reports that another solar eclipse was observed in Sparta during the next year, on August 1, 477 BC. As part of her title, Underwood gained a recording contract with Arista Records; her first single, "Inside Your Heaven", was released on June 14, 2005. An annular eclipse of the Sun occurred at Sardis on February 17, 478 BC, while Xerxes was departing for his expedition against Greece, as Herodotus, VII, 37 recorded ([Hind and Chambers, 1889: 323] considered this absolute date more than a century ago). During the season, Constantine Maroulis tried to flirt with her but she refused to go out with him. One likely candidate took place on May 28, 585 BC, probably near the Halys river in the middle of modern Turkey. On her last song of the night in the final two, Carrie's spectacular performance of "Angels Brought Me Here" had Simon saying, "I think you've done enough to win the competition." On May 25, 2005, she became the fourth winner of American Idol, beating Southern rocker Bo Bice, and she joins Kelly Clarkson and Clay Aiken as the only contestants who have never been one of the "bottom three" singers during any week's results. Exactly which eclipse was involved has remained uncertain, although the issue has been studied by hundreds of ancient and modern authorities. I will make a prediction, not only will you win this competition, but you will sell more records than any other previous 'Idol' winner." Cowell went on to say on the March 30 show that she has the "it factor" that will make her a star.

Soldiers on both sides put down their weapons and declared peace as a result of the eclipse. On the March 22 show, after a performance of Heart's "Alone", Simon Cowell said, "Carrie, you're not just the girl to beat, you're the person to beat. Herodotus wrote that Thales of Milete predicted an eclipse which occurred during a war between the Medians and the Lydians. After singing Martina McBride's "Independence Day" Simon Cowell said he couldn't believe no one has discovered her yet. For a discussion, see the text by Stephenson. She can also play piano and yodel, the latter of which was demonstrated on the Tonight Show the night after she won. There have been other claims to date earlier eclipses, in Babylon and also in China, but these are highly disputed and rely on much supposition. On the April 20 elimination show, Underwood demonstrated her ability to play the guitar.

This is the earliest solar eclipse that can be exactly dated. Underwood's musical influences include pop, but are predominantly country; she stated during Idol auditions that her favorite singer is Martina McBride. A solar eclipse of 15 June 763 BC mentioned in an Assyrian text is important for the Chronology of the Ancient Orient. She also competed in numerous beauty pageants at the university and was selected as Miss NSU runner-up in 2004. After a Saros cycle finishes, a new Saros cycle begins 1 Inex later (hence its name: in-ex). Underwood attended Northeastern State University, where she majored in mass communication and is a member of Sigma Sigma Sigma sorority. The Inex cycle is itself a poor cycle, but it is very convenient in the classification of eclipse cycles. Underwood graduated from Checotah High School in 2001 as salutatorian.

The Saros cycle is probably the most well known, and one of the best, eclipse cycles. At the age of 13, her manager at the time tried to get a recording contract at Capitol Records, but due to management changes at Capitol it never materialized. Two such cycles are the Saros and the Inex. Carrie Underwood was born in Muskogee, Oklahoma and raised in a farm in Checotah, Oklahoma. If the date and time of a solar eclipse is known, it is possible to predict other eclipses using eclipse cycles. . Normally this is not visible because the photosphere is much brighter than the corona. Carrie Marie Underwood (born March 10, 1983) is an American country singer who rose to fame as the winner of the fourth season of American Idol.

For astronomers, a total solar eclipse forms a rare opportunity to observe the corona (the outer layer of the Sun's atmosphere). Top-Selling Country Single of the Year: "Inside Your Heaven/Independence Day," Carrie Underwood (Won). (eclipse predictions by Fred Espenak, NASA/GSFC.). Country Single Sales Artist of the Year: Carrie Underwood (Won). The longest total solar eclipse during the 8,000-year period from 3000 BC to 5000 AD will occur on July 16, 2186, when totality will last 7 min 29 s. Top-Selling Hot 100 Song of the Year: "Inside Your Heaven/Independence Day," Carrie Underwood (Won). The next eclipse of comparable duration will not occur until June 25, 2150. Final Results Show (post-win performance of first single) - "Inside Your Heaven".

Observers aboard a Concorde aircraft were able to stretch totality to about 74 minutes by flying along the path of the Moon's umbra. Final Results Show (performance with Rascal Flatts) - "Bless the Broken Road". The last time this happened was June 30, 1973. Final Results Show (duet with Bo Bice) - "Up Where We Belong" (O.A.: Jennifer Warnes and Joe Cocker). During each millennium there are typically fewer than 10 total solar eclipses exceeding 7 minutes. Finals Top 2 Performance 3 (song originally written for Australian Idol) - "Angels Brought Me Here" (O.A.: Guy Sebastian). Totality can never last more than 7 min 40 s, and is usually much shorter. Finals Top 2 Performance 2 (favorite from season) - "Independence Day" (O.A.: Martina McBride).

Then, after waiting so long, the total eclipse only lasts for a few minutes, as the Moon's umbra moves eastward at over 1700 km/h. Finals Top 2 Performance 1 (new song written for AI) - "Inside Your Heaven". Although they occur somewhere on Earth approximately every 18 months, it has been estimated that they recur at any given place only once every 370 years, on average (Stephenson, p.54). Finals Top 3 Performance 3 (Judges' choice) - "Man! I Feel Like a Woman!" (O.A.: Shania Twain). Total solar eclipses are rare events. Finals Top 3 Performance 2 (Performer's choice) - "Making Love out of Nothing at All" (O.A.: Air Supply). Outside of the central track, a partial eclipse can usually be seen over a much larger area of the Earth. Finals Top 3 Performance 1 (Clive Davis' choice) - "Crying" (O.A.: Roy Orbison).

In the most favourable circumstances, when a total eclipse occurs very close to perigee, the track can be over 250 km wide and the duration of totality may be over 7 minutes. Finals Top 4 Performance 2 (Gamble and Huff Songs) - "If You Don't Know Me by Now" (O.A.: Harold Melvin & the Blue Notes). The width of the track of a central eclipse varies according to the relative apparent diameters of the Sun and Moon. Finals Top 4 Performance 1 (Nashville Songs) - "Sin Wagon" (O.A.: The Dixie Chicks). The Earth is also rotating from west to east, but the umbra always moves faster than any given point on the Earth's surface, so it almost always appears to move in a roughly west-east direction across a map of the Earth (there are some rare exceptions to this which can occur during an eclipse of the midnight sun in arctic or antarctic regions). Finals Top 5 Performance 2 (Billboard top 40) - "Bless the Broken Road" (O.A.: Rascal Flatts' version of Marcus Hummon's "Bless the Broken Road"). During a central eclipse, the Moon's umbra (or antumbra, in the case of an annular eclipse) moves rapidly from west to east across the Earth. Finals Top 5 Performance 1 (Leiber and Stoller Songs) - "Trouble" (O.A.: Elvis Presley).

However, some are visible only as partial eclipses, because the umbra passes either above or below the earth, and others are central only in remote regions of the arctic or antarctic. Finals Top 6 Performance (Songs of the 21st Century) - "When God Fearin' Women Get the Blues" (O.A.: Martina McBride). This means that in any given year, there will always be at least two solar eclipses, and there can be as many as five. Finals Top 7 Performance (70's Dance Music) - "MacArthur Park" (O.A.: Donna Summer's version of Richard Harris' hit). Sometimes the New Moon occurs close enough to a node during two consecutive months. Finals Top 8 Performance (Songs from Contestants' Birthyear) - "Love Is a Battlefield" (O.A.: Pat Benatar). Therefore, the New Moon occurs close to the nodes at two periods of the year approximately six months apart, and there will always be at least one solar eclipse during these periods. Finals Top 9 Performance (Broadway Musicals) - "Hello Young Lovers" (O.A.: Johnny Mathis).

The Moon's orbit intersects with the ecliptic at the two nodes that are 180 degrees apart. Finals Top 10 Performance (Songs of the 90's) - "Independence Day" (O.A.: Martina McBride). The time between one perigee and the next is known as the anomalistic month. Finals Top 11 Performance (Billboard #1's) - "Alone" (O.A.: Heart). Finally, the Moon's perigee is moving forwards in its orbit, and makes a complete circuit in about 9 years. Finals Top 12 Performance (Songs of the 60's) - "When Will I Be Loved" (O.A.: The Everly Brothers). This period is called the draconitic month. Semi-Final Performance 3 (Women Top 8) - "Because You Love Me" (O.A.: Jo Dee Messina).

This means that the time between each passage of the Moon through the ascending node is slightly shorter than the sidereal month. Semi-Final Performance 2 (Women Top 10) - "Piece of My Heart" (O.A.: Faith Hill's version of Janis Joplin's classic). However, the nodes of the Moon's orbit are gradually moving in a retrograde motion, due the the action of the Sun's gravity on the Moon's motion, and they make a complete circuit every 18.5 years. Semi-Final Performance 1 (Women Top 12) - "Could've Been" (O.A.: Tiffany). The Moon crosses from south to north of the ecliptic at its ascending node. Hollywood 2 - "Independence Day" (O.A.: Martina McBride). This is known as the synodic month, and corresponds to what is commonly called the lunar month. Hollywood 1 - "Young Hearts (Run Free)" (O.A.: Candi Staton)".

This means that the average time between one New Moon and the next is longer, and is approximately 29.6 days. Louis Auditions - "I Can't Make You Love Me" (Original Artist: Bonnie Raitt). However, during one sidereal month, the Earth has moved on in its orbit around the Sun. St. This is known as the sidereal month. The Moon orbits the Earth in approximately 27.3 days, relative to a fixed frame of reference.

It is only when the Moon is closer to the Earth than average (near its perigee) that a total eclipse occurs. On average, the Moon appears to be slightly smaller than the Sun, so the majority (about 60%) of central eclipses are annular. This means that the apparent size of the Moon is sometimes larger or smaller than average, and it is this effect that leads to the difference between total and annular eclipses (the distance of the Earth from the Sun also varies during the year, but this is a smaller effect). The Moon's orbit is also elliptical, which means that the distance of the Moon from the Earth can vary by about 6% from its average value.

A solar eclipse can occur only when the New Moon occurs close to one of the points (known as nodes) where the Moon's orbit crosses the ecliptic – hence the name. Because of this, at the time of a New Moon, the Moon will usually pass above or below the Sun. The Moon's orbit around the Earth is inclined at an angle of just over 5 degrees to the plane of the Earth's orbit around the Sun (the ecliptic). The larger light gray area is the penumbra, in which a partial eclipse will be seen.

The small area where the umbra touches the Earth's surface is where a total eclipse will be seen. The dark gray region to the right of the moon is the umbra, where the Sun is completely obscured by the Moon. The diagram to the right shows the alignment of the Sun, Moon and Earth at a solar eclipse. For more information on safe eclipse viewing, see:.

Note that it is never safe to look at an annular or partial eclipse directly, because the Sun's disk is never completely covered during this type of eclipse. The exact time and duration of totality for the location from which the eclipse is being observed should be determined from a reliable source (local astronomers, etc.). However, it is important to stop directly viewing the Sun promptly at the end of totality. The Sun's faint corona will be visible, and even the chromosphere, solar prominences, and possibly even a solar flare may be seen.

Contrary to popular belief, it is safe to observe the total phase of a total solar eclipse directly with the unaided eye, binoculars or a telescope, when the Sun's photosphere is completely covered by the Moon; indeed, this is a very spectacular and beautiful sight, and it is too dim to be seen through filters. These precautions apply to viewing the Sun at any time except during the totality phase of a total solar eclipse (see below). The optical viewfinders provided with some video and digital cameras are not safe. Viewing the Sun's disk on a video display screen (provided by a video camera or digital camera) is safe, although the camera itself may be damaged by direct exposure to the Sun.

However, care must be taken to ensure that no one looks through the projector (telescope, pinhole, etc.) directly. The projected image of the Sun can then be safely viewed; this technique can be used to observe sunspots, as well as eclipses. This can be done by projecting an image of the disk onto a white piece of paper or card using a pair of binoculars (with one of the lenses covered), a telescope, or another piece of cardboard with a small hole in it (about 1 mm diameter), often called a pinhole camera. The safest way to view the Sun's disk is by indirect projection.

Only properly designed and certified solar filters should ever be used for direct viewing of the Sun's disk. Sunglasses are not safe, since they do not block the harmful and invisible infrared radiation which causes retinal damage. The Sun's disk can be viewed using appropriate filtration to block the harmful part of the Sun's radiation. Viewing the Sun during partial and annular eclipses (and during total eclipses outside the brief period of totality) requires special eye protection, or indirect viewing methods.

Viewing the Sun's disk through any kind of optical aid (binoculars, a telescope, or even an optical camera viewfinder) is even more hazardous, although just viewing it with the naked eye can easily cause damage. Unfortunately, looking at the Sun during an eclipse is just as dangerous as looking at it outside an eclipse, except during the brief period of totality, when the Sun's disk is completely covered (totality occurs only during a total eclipse and only very briefly—it does not occur during a partial or annular eclipse). However, during an eclipse, with so much of the Sun covered, it is easier and more tempting to stare at it. Under normal conditions, the Sun is so bright that it's difficult to stare at it directly, so there is no tendency to look at it in a way that might damage the eye.

The retina has no sensitivity to pain, and the effects of retinal damage may not appear for hours, so there is no warning that injury is occurring. This damage can result in permanent impairment of vision, up to and including blindness. Looking directly at the photosphere of the Sun (the bright disk of the Sun itself), even for just a few seconds, can cause permanent damage to the retina of the eye, because of the intense visible and invisible radiation that the photosphere emits. When the Moon disappears at Full Moon by passing into Earth's shadow, the event is properly called an eclipse, but when the Moon passes in front of the Sun, we see an occultation of the Sun by the Moon.

Properly speaking, an eclipse occurs when one object passes into the shadow cast by another object. The term eclipse is actually a misnomer: The phenomenon of the Moon passing in front of the Sun is actually an occultation. Slightly more annular eclipses than total eclipses occur, because on average the Moon lies too far away from Earth to cover the Sun completely. Hence the term annular eclipse.

In that case, at the time of greatest eclipse there remains a thin annulus (or ring) of brilliant Sun left uncovered. When a solar eclipse occurs when the Moon is at or near apogee, however, it appears smaller, and it cannot cover the Sun completely. When a solar eclipse occurs when the Moon is at or near perigee, it appears large enough to cover the bright disk, or photosphere, of the Sun completely, and a total eclipse occurs. The furthest point in the orbit is referred to as apogee, and the closest point is called perigee.

Because the Moon's orbit around Earth is an ellipse rather than a circle, however, at some times during the month the Moon is further away, and at other times it is closer to Earth, than average. As seen from Earth, therefore, the Sun and the Moon appear to be about the same size in the sky - about 1/2 of a degree in angular measure. One of the most remarkable co-incidences in nature is that (i) the Sun lies about 400 times as far from Earth as does the Moon, and (ii) the Sun is also about 400 times the diameter of the Moon. The reason why some solar eclipses are total and others are annular has to do with the elliptical nature of the Moon's orbit around Earth.

There are four types of solar eclipses:. . A total solar eclipse is considered by many to be the most spectacular natural phenomenon that one can observe. This configuration can only occur at New Moon, when the Sun and Moon are in conjunction, as seen from Earth.

A solar eclipse occurs when the Moon passes in front of the Sun and obscures it totally or partially. February 16, 1980: Launch of rockets from San Marco platform. February 26, 1979: Launch of rockets from Red Lake, Canada. November 12, 1966: Launch of two Titus-rockets fom Las Palmas, Argentina.

May 20, 1966: Launch of rockets at Karystos, Greece to watch the solar eclipse. May 30, 1965: Launch of rockets at Charlestown, USA. MacRobert, Sky & Telescope magazine. How to Watch a Partial Solar Eclipse Safely, Alan M.

Eye Safety During Solar Eclipses, Fred Espenak, NASA Goddard Space Flight Center. However, some eclipses can only be seen as a partial eclipse, because the central line never intersects the Earth's surface. This phenomenon can usually be seen from a large part of the Earth outside of the track of a central eclipse. A partial eclipse occurs when the Sun and Moon are not exactly in line, and the Moon only partially obscures the Sun.

The generic term for a total, annular or hybrid eclipse is a central eclipse. At some points on the Earth it is visible as a total eclipse; whereas at others it is annular. A hybrid eclipse is intermediate between a total and annular eclipse. Hence the Sun appears as a very bright ring surrounding the outline of the Moon.

An annular eclipse occurs when the Sun and Moon are exactly in line, but the apparent size of the Moon is smaller than that of the Sun. During any one eclipse, a total eclipse is visible only from a fairly narrow track on the surface of the Earth. The intensely bright disk of the Sun is replaced by the dark outline of the Moon, and the much fainter corona is visible (see image right). A total eclipse occurs when the Sun is completely obscured by the Moon.