Corona Borealis is a small constellation in the Northern Celestial Hemisphere. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, remains one of the 88 modern constellations, its brightest stars form a semicircular arc. Its Latin name, inspired by its shape, means "northern crown". In classical mythology Corona Borealis represented the crown given by the god Dionysus to the Cretan princess Ariadne and set by him in the heavens. Other cultures likened the pattern to a circle of elders, an eagle's nest, a bear's den, or a smokehole. Ptolemy listed a southern counterpart, Corona Australis, with a similar pattern; the brightest star is the magnitude 2.2 Alpha Coronae Borealis. The yellow supergiant R Coronae Borealis is the prototype of a rare class of giant stars—the R Coronae Borealis variables—that are hydrogen deficient, thought to result from the merger of two white dwarfs. T Coronae Borealis known as the Blaze Star, is another unusual type of variable star known as a recurrent nova.
Of magnitude 10, it last flared up to magnitude 2 in 1946. ADS 9731 and Sigma Coronae Borealis are multiple star systems with six and five components respectively. Five star systems have been found to have Jupiter-sized exoplanets. Abell 2065 is a concentrated galaxy cluster one billion light-years from the Solar System containing more than 400 members, is itself part of the larger Corona Borealis Supercluster. Covering 179 square degrees and hence 0.433% of the sky, Corona Borealis ranks 73rd of the 88 modern constellations by area. Its position in the Northern Celestial Hemisphere means that the whole constellation is visible to observers north of 50°S, it is bordered by Boötes to the north and west, Serpens Caput to the south, Hercules to the east. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "CrB"; the official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of eight segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 15h 16.0m and 16h 25.1m, while the declination coordinates are between 39.71° and 25.54°.
It has a counterpart—Corona Australis—in the Southern Celestial Hemisphere. The seven stars that make up the constellation's distinctive crown-shaped pattern are all 4th-magnitude stars except for the brightest of them, Alpha Coronae Borealis; the other six stars are Theta, Gamma, Delta and Iota Coronae Borealis. The German cartographer Johann Bayer gave twenty stars in Corona Borealis Bayer designations from Alpha to Upsilon in his 1603 star atlas Uranometria. Zeta Coronae Borealis was noted to be a double star by astronomers and its components designated Zeta1 and Zeta2. John Flamsteed did with Nu Coronae Borealis, he named them 20 and 21 Coronae Borealis in his catalogue, alongside the designations Nu1 and Nu2 respectively. Chinese astronomers deemed nine stars to make up the asterism, adding Rho Coronae Borealis. Within the constellation's borders, there are 37 stars brighter than or equal to apparent magnitude 6.5. Alpha Coronae Borealis appears as a blue-white star of magnitude 2.2. In fact, it is an Algol-type eclipsing binary that varies by 0.1 magnitude with a period of 17.4 days.
The primary is a white main-sequence star of spectral type A0V, 2.91 times the mass of the Sun and 57 times as luminous, is surrounded by a debris disk out to a radius of around 60 astronomical units. The secondary companion is a yellow main-sequence star of spectral type G5V, a little smaller the diameter of the Sun. Lying 75±0.5 light-years from Earth, Alphecca is believed to be a member of the Ursa Major Moving Group of stars that have a common motion through space. Located 112±3 light-years away, Beta Coronae Borealis or Nusakan is a spectroscopic binary system whose two components are separated by 10 AU and orbit each other every 10.5 years. The brighter component is a oscillating Ap star, pulsating with a period of 16.2 minutes. Of spectral type A5V with a surface temperature of around 7980 K, it has around 2.1 M☉, 2.6 solar radii, 25.3 L☉. The smaller star is of spectral type F2V with a surface temperature of around 6750 K, has around 1.4 M☉, 1.56 R☉, between 4 and 5 L☉. Near Nusakan is Theta Coronae Borealis, a binary system that shines with a combined magnitude of 4.13 located 380±20 light-years distant.
The brighter component, Theta Coronae Borealis A, is a blue-white star that spins rapidly—at a rate of around 393 km per second. A Be star, it is surrounded by a debris disk. Flanking Alpha to the east is Gamma Coronae Borealis, yet another binary star system, whose components orbit each other every 92.94 years and are as far apart from each other as the Sun and Neptune. The brighter component has been classed as a Delta Scuti variable star, though this view is not universal; the components are main sequence stars of spectral types B9V and A3V. Located 170±2 light-years away, 4.06-magnitude Delta Coronae Borealis is a yellow giant star of spectral type G3.5III, around 2.4 M☉ and has swollen to 7.4 R☉. It has a surface temperature of 5180 K. For most of its existence, Delta Coronae Borealis was a blue-white main-sequence star of spectral type B before it ran out of hydrogen fuel in its core, its luminosity and spectrum suggest it has just crossed the Hertzsprung gap, having finished burning core hydrogen and just begun burning hydrogen in a shell that surrounds the core.
Zeta Coronae Borealis is a double star with two blue-white components
That's All, Brother is a Douglas C-47 Skytrain aircraft that led the formation of 800 others from which 13,000 U. S. paratroopers jumped on D-Day, June 6, 1944, the beginning of the liberation of France in the last two years of World War II. After the war it was returned to the United States and sold to civilian owners falling victim to neglect until it was found in an Oshkosh, boneyard in 2015, facing imminent disassembly to be converted into a modern turbine aircraft, it is part of the Commemorative Air Force. The C-47's name, painted on its nose, was chosen by Air Force Lt. Col. John M. Donalson, commander of the 87th Fighter-Bomber Squadron, who flew the plane during the operation, as a "message to Adolf Hitler" that Nazi Germany's days were numbered, it was flown again in 2018, has been exhibited at air shows. After further refitting it has been flown across the Atlantic with other historic aircraft that took part in the invasion, to commemorate its 75th anniversary; when the war began, John Donalson, who flew with the Alabama-based 106th Observation Squadron, assigned to the Pacific theater during the war, was transferred to Europe.
He flew a Douglas C-47 Skytrain that he had named Belle of Birmingham, in honor of his home state's largest city. But for Operation Overlord, the 1944 invasion of Normandy which opened the western front, it was necessary to cut holes in the plane's fuselage for extra equipment. Donalson, by commanding the 438th Troop Carrier Group of the 87th Troop Carrier Squadron, part of IX Troop Carrier Command, so he was issued another C-47 to lead the formation of those aircraft which dropped paratroopers onto the shores of France; the C-47 issued to Donalson had been built three months earlier at the Douglas Aircraft plant in Oklahoma City. It was delivered the day after completion to what was the United States Army Air Forces at Love Field in Dallas. Five weeks it was flown to England by the Air Transport Command. Donalson named his new plane That's All, Brother, as a personal message to Adolf Hitler that Nazi Germany's dominance of Europe would soon be ended. On the morning of June 6, That's All, Brother led 800 planes that dropped over 13,000 American paratroopers onto the French coast.
It was chosen for the job because it had been equipped with radar that could find the beacons dropped as "pathfinders" to mark drop zones by an earlier group of paratroopers. Allied troops held their beachhead despite heavy initial losses, began liberating France; the C-47 was used in other operations in Western Europe that year, including Market Garden, Repulse, in 1945's Operation Varsity, part of the invasion of Germany. By the end of the war, the plane had been decommissioned, it was sold on the civilian market as surplus. During the decades after the war it passed through 12 private owners, who kept it in good condition, never crashing or damaging it as they put it to a variety of uses, although none of them were aware of its historic importance, it was modified into a more conventional DC-3 configuration and painted in a scheme common to such craft during the Vietnam War. The plane's rediscovery began in 2006; that year Staff Sgt. Matthew Scales, assigned to the 106th, began researching the unit's history.
Most of that focused on the squadron's work in the South Pacific, but he learned that a member of the 106th had flown the lead plane on D-Day. "I didn't understand how this was possible, as, on June 6, 1944, my squadron was about as far away from Normandy as humanly possible," he recalled later. The next year Scales transferred to the Air Force Historical Research Agency to better do his research, he found the records of Donalson's transfer from the 106th to fly the D-Day C-47s. Along with those records was That's All, Brother's military serial number as well as the tail number it had borne as a civilian aircraft, allowing him to track it to its owner in Mesa, Arizona. Scales thought the man's plane was the Belle of Birmingham, Donalson's usual aircraft; the current owner had restored it to airworthiness, promised to keep it in good condition when he learned of its historic importance. Scales learned of its true identity, called the owner back. By however, it had been sold to Basler Turbo Conversions of Oshkosh, Wisconsin, to be converted into a BT-67, one of four the company makes from the old DC-3s every year, a process which leaves only 30% of the original craft and scraps the rest.
The owner had flown it to Wittman Regional Airport. The company had put it in their boneyard to await the procedure, which it was scheduled to begin within six months. After the plane's serial number was found, proving it was That's All, stories were published. Organizations and private collectors called; the Commemorative Air Force, an organization which restores and flies vintage planes to exhibit at air shows, took possession of the C-47. The CAF set itself the goal of restoring the aircraft not only to the point of airworthiness but having it participate in the D-Day 75th anniversary ceremonies in 2019. While the organization's Minnesota Wing provided sufficient volunteer labor to assist the experts at Basler, it needed money as well. In 2015, after the rediscovered plane was put on public display for the first time at the EAA AirVenture Oshkosh air show, a CAF executive started a Kickstarter campaign.
The Smradlivo Lake is a glacial lake located in the central section of the Rila mountain range, south-western Bulgaria. It is the second of the five Smradlivi Lakes and is situated at an altitude of 2,298 m in a hanging valley facing the valley of the Rilska River to the north between the summits of Rilets to the south-west and Kyoravitsa to the south, it falls within the boundaries of the Rila Monastery Nature Park. The Smradlivo Lake is oval shaped with a maximum length of 900 m the width of 260 m. With a surface area of 212,000 m² it is the largest glacial lake in Bulgaria and the Balkan Peninsula, its depth reaches 24 m. Its outflow is at the northern end, forming a stream that flows into the Rilska River, a left tributary of the Struma, after 1.2 km. Along its northern shore there is a small dyke to regulate the outflow to the small Rilska cascade; the waters of the Smradlivo Lake have high content of oxygen and low oxidisability. It sustains populations of brown trout and due to its remoteness there are brown bears and red deer roaming the forests in the vicinity of the lake.
In Bulgarian language the name of the lake means the Stinking Lake. Many legends about the lake are linked with the 10th-century medieval Bulgarian hermit and saint John of Rila who found refuge in the nearby valleys and established the Rila Monastery. Мичев, Николай. Географски речник на България. София: Наука и култура. Yankov, Petar. Rila Monastery Nature Park. Management Plan 2004–2013. Sofia: Ministry of Environment and Water