Colin Leonhardt/Birdseye View Photography
あなたはもしかすると、二重の虹を見たことがあるかもしれない。けれども、普通の半円ではない、「全円の虹」はどうだろう？
上の「全円の虹」は、2013年に、オーストラリアのパース近くにある海岸上空で、ヘリコプターから撮影されたものだ。
NASAは「Astronomy Picture of the Day」というサイトで、毎日1枚ずつ、宇宙や気象の画像を紹介しており、この写真は同サイトで9月30日付けで公開されたものだ（撮影は、オーストラリアの写真家コリン・レオンハート氏）。
NASAの解説によると、「地上からはふつう、虹の上半分しか見えません。けれども上空からは、360度丸い虹をしばしば見ることができます」とのことだ（正確には、これは通常の虹とは原理が異なる、ブロッケン現象によるものだという）。
ヘリコプターは、沈み行く太陽と、土砂降りの雨の間を飛行していた。この虹色の輪は、およそ5キロメートルの飛行中ずっと、ヘリコプターから観察できたという。
画像では、はっきりした輪の外側に、光の薄い二番目の輪があるのも見ることができる。二番目の輪のほうは、色の並び方が反対であることにも注目してほしい。
[Dominique Mosbergen(English) 日本語版：ガリレオ]
「世界の虹」写真集
Thunderstorm Sweeps Through Las Vegas(01 of17)
LAS VEGAS, NV - SEPTEMBER 09: A rainbow appears over an air traffic control tower under construction at McCarran International Airport on September 9, 2013 in Las Vegas, Nevada. A monsoon thunderstorm swept across the area causing power outages and flooding. Flights at McCarran were grounded for about an hour because fueling operations were halted as a result of lightning from the storm. (Photo by Ethan Miller/Getty Images) (credit:Getty Images)
Pittsburgh Pirates v Colorado Rockies(02 of17)
DENVER, CO - AUGUST 10: Fans return to their seats under a rainbow after a storm forced he evacutation of the upper deck and delayed the start of the game between the Pittsburgh Pirates and the Colorado Rockies at Coors Field on August 10, 2013 in Denver, Colorado. (Photo by Doug Pensinger/Getty Images) (credit:Getty Images)
Peterborough United v Hull City - Pre Season Friendly(03 of17)
PETERBOROUGH, ENGLAND - JULY 29: Peterborough United players warm up at half time underneath a rainbow during the pre season friendly match between Peterborough United and Hull City at London Road Stadium on July 29, 2013 in Peterborough, England. (Photo by David Rogers/Getty Images) (credit:Getty Images)
AFL Rd 15 - Melbourne v Sydney(04 of17)
MELBOURNE, AUSTRALIA - JULY 07: Chris Dawes of the Demons and Ted Richards of the Swans compete for the ball as a double rainbow appears above the ground during the round 15 AFL match between the Melbourne Demons and the Sydney Swans at Melbourne Cricket Ground on July 7, 2013 in Melbourne, Australia. (Photo by Scott Barbour/Getty Images) (credit:Getty Images)
New York Yankees v Baltimore Orioles(05 of17)
BALTIMORE, MD - JUNE 28: A rainbow shines in the sky as pitcher Kevin Gausman #37 of the Baltimore Orioles works batter Alberto Gonzalez #40 of the New York Yankees in the fourth inning at Oriole Park at Camden Yards on June 28, 2013 in Baltimore, Maryland. (Photo by Patrick Smith/Getty Images) (credit:Getty Images)
AFL Rd 13 - Fremantle v North Melbourne(06 of17)
PERTH, AUSTRALIA - JUNE 23: A general view of play as a rainbow appears during the round 13 AFL match between the Fremantle Dockers and the North Melbourne Kangaroos at Patersons Stadium on June 23, 2013 in Perth, Australia. (Photo by Paul Kane/Getty Images) (credit:Getty Images)
Bodies Of Two Army Soldiers Killed In Afghanistan By Suicide Bomber Return To Dover AFB(07 of17)
DOVER, DE - JUNE 06: A rainbow is seen in the sky over the chairs in where family members will sit before U.S. Army soldiers carry the flag-draped transfer cases containing the remains of U.S. Army 2nd Lt. Justin L. Sisson and U.S. Army Spc. Robert A. Pierce during a dignified transfer at Dover Air Force Base, on June 6, 2013 in Dover, Delaware. According to reports, Sisson and Pierce, both assigned to the 1st Battalion, 506th Infantry Regiment, 4th Brigade Combat Team, 101st Airborne Division, in Fort Campbell, Ky., were killed by a suicide vehicle-borne improvised explosive device while supporting Operation Enduring Freedom - Afghanistan. (Photo by Patrick Smith/Getty Images) (credit:Getty Images)
Aerials of U.S.-Canada Border Along The Niagara River(08 of17)
NIAGARA FALLS, NY - JUNE 04: A rainbow appears in a cloud of mist rising over Horseshoe Falls, the largest of the Niagara Falls on June 4, 2013 at Niagara Falls, New York. The falls, which have a combined highest flow rate of any waterfalls in the world, stradle the U.S.-Canada border, drawn through the Niagara River, which drains Lake Erie into Lake Ontario. The falls, visited by millions of tourists on each side of the border, are also a major source of hydroelectric power for the region. The aerial view was seen from a helicopter flown by the U.S. Office of Air and Marine, (OAM), which monitors and patrols the U.S. northern border with Canana. (Photo by John Moore/Getty Images) (credit:Getty Images)
Bavarian Villages Mark Ascension With Processions(09 of17)
GRASSAU, GERMANY - MAY 09: A rainbow is seen over the fields and mountains prior to an Ascension Day procession on May 9, 2013 in Grassau, Germany. Ascension is an ecumenical feast that commemmorates the ascension of Jesus Christ to Heaven. Bavaria, in contrast to the rest of Germany, is heavily Catholic, and the religious calendar plays a strong role in its deeply-ingrained folk traditions. (Photo by Lennart Preiss/Getty Images) (credit:Getty Images)
Sony Open in Hawaii - Second Round(10 of17)
HONOLULU, HI - JANUARY 11: A rainbow over the ocean during the second round of the Sony Open in Hawaii at Waialae Country Club on January 11, 2013 in Honolulu, Hawaii. (Photo by Christian Petersen/Getty Images) (credit:Getty Images)
Sony Open in Hawaii - Second Round(11 of17)
HONOLULU, HI - JANUARY 11: A rainbow over the ocean during the second round of the Sony Open in Hawaii at Waialae Country Club on January 11, 2013 in Honolulu, Hawaii. (Photo by Christian Petersen/Getty Images) (credit:Getty Images)
Sony Open in Hawaii - Second Round(12 of17)
HONOLULU, HI - JANUARY 11: A rainbow over the 17th hole green during the second round of the Sony Open in Hawaii at Waialae Country Club on January 11, 2013 in Honolulu, Hawaii. (Photo by Christian Petersen/Getty Images) (credit:Getty Images)
Hyundai Tournament of Champions - Round One(13 of17)
KAPALUA, HI - JANUARY 07: Dustin Johnson (L) hits a tee shot under a partial rainbow on the 13th hole during the replay of the first round of the Hyundai Tournament of Champions at the Plantation Course on January 7, 2013 in Kapalua, Hawaii. (Photo by Christian Petersen/Getty Images) (credit:Getty Images)
Hyundai Tournament of Champions - Round One(14 of17)
KAPALUA, HI - JANUARY 05: A rainbow is seen during the replay of the first round of the Hyundai Tournament of Champions at the Plantation Course on January 5, 2013 in Kapalua, Hawaii. (Photo by Christian Petersen/Getty Images) (credit:Getty Images)
Hyundai Tournament of Champions - Round One(15 of17)
KAPALUA, HI - JANUARY 05: A rainbow is seen over the Plantation Course during a weather delay before the replay of the first round of the Hyundai Tournament of Champions at on January 5, 2013 in Kapalua, Hawaii. (Photo by Christian Petersen/Getty Images) (credit:Getty Images)
Hyundai Tournament of Champions - Round One(16 of17)
KAPALUA, HI - JANUARY 05: A rainbow during the replay of the first round of the Hyundai Tournament of Champions at the Plantation Course on January 5, 2013 in Kapalua, Hawaii. (Photo by Christian Petersen/Getty Images) (credit:Getty Images)
FC St. Pauli v MSV Duisburg - 2. Bundesliga(17 of17)
HAMBURG, GERMANY - NOVEMBER 25: A rainbow appears during the second Bundesliga match between FC St. Pauli and MSV Duisburg at Millerntor Stadium on November 25, 2012 in Hamburg, Germany. (Photo by Stuart Franklin/Bongarts/Getty Images) (credit:Getty Images)
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