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96-477: The spirit has several regional names: The Soucouyant is a folklore character who appears as a reclusive old woman (or man) by day. By night, they strip off their wrinkled skin and put it in a mortar. In the form of a fireball , they fly across the dark sky in search of a victim. The Soucouyants can enter the home of their victim through any sized hole such as cracks and keyholes. Soucouyants suck humans' blood from their arms, necks, legs and other soft regions while

192-475: A black body gives the value for luminosity for a black body, an idealized object which is perfectly opaque and non-reflecting: L = σ A T 4 , {\displaystyle L=\sigma AT^{4},} where A is the surface area, T is the temperature (in kelvins) and σ is the Stefan–Boltzmann constant , with a value of 5.670 374 419 ... × 10  W⋅m ⋅K . Imagine

288-477: A lightning bolt , and is a phenomenon distinct from St. Elmo's fire . Some 19th-century reports describe balls that eventually explode and leave behind an odor of sulfur. Descriptions of ball lightning appear in a variety of accounts over the centuries and have received attention from scientists . An optical spectrum of what appears to have been a ball lightning event was published in January 2014 and included

384-532: A photometric system . Several different photometric systems exist. Some such as the UBV or Johnson system are defined against photometric standard stars, while others such as the AB system are defined in terms of a spectral flux density . A star's luminosity can be determined from two stellar characteristics: size and effective temperature . The former is typically represented in terms of solar radii , R ⊙ , while

480-408: A 1 Jy signal from a radio source at a redshift of 1, at a frequency of 1.4 GHz. Ned Wright's cosmology calculator calculates a luminosity distance for a redshift of 1 to be 6701 Mpc = 2×10 m giving a radio luminosity of 10 × 4 π (2×10 ) / (1 + 1) = 6×10 W Hz . To calculate the total radio power, this luminosity must be integrated over the bandwidth of the emission. A common assumption

576-402: A 10   W transmitter at a distance of 1 million metres, radiating over a bandwidth of 1 MHz. By the time that power has reached the observer, the power is spread over the surface of a sphere with area 4 πr or about 1.26×10 m , so its flux density is 10 / 10 / (1.26×10 ) W m Hz = 8×10 Jy . More generally, for sources at cosmological distances, a k-correction must be made for

672-457: A ball of lightning entered the kitchen of a house in the village of Salagnac in the valley of Correze . This ball rolled across without doing any harm to two women and a young man who were here; but on getting into an adjoining stable it exploded and killed a pig which happened to be shut up there, and which, knowing nothing about the wonders of thunder and lightning, dared to smell it in the most rude and unbecoming manner. The motion of such balls

768-509: A blast of wind from the open door blew out the flame of the candles which were lit in front of the iconostasis , there was a long clap of thunder, louder than before, and I suddenly saw a fiery ball flying from the window straight towards the head of the Emperor. The ball (it was of lightning) whirled around the floor, then passed the chandelier and flew out through the door into the park. My heart froze, I glanced at my grandfather – his face

864-401: A dazzling globe of electric fire, apparently between six and twelve inches [15 and 30 cm] in diameter, was stationary about six inches [15 cm] below and to the right of my right knee. As I looked at it, it exploded with a sharp report quite impossible to confuse with the continuous turmoil of the lightning, thunder and hail, or that of the lashed water and smashed wood which was creating

960-572: A few tens of R ⊙ . For example, R136a1 has a temperature over 46,000 K and a luminosity of more than 6,100,000 L ⊙ (mostly in the UV), it is only 39  R ☉ (2.7 × 10   m ). The luminosity of a radio source is measured in W Hz , to avoid having to specify a bandwidth over which it is measured. The observed strength, or flux density , of a radio source is measured in Jansky where 1 Jy = 10 W m Hz . For example, consider

1056-550: A hag enters your house, she always shed her skin. When you first see her, she appears like the flame of a candle floating about; in some way, she puts you to sleep, and resumes her body (but without the skin); she then lies on you, and sucks away every drop of blood that God has put in you." There are more references to the Bahamian Hag in Folk-tales of Andros Island, Bahamas, published in 1918 by Elsie Clews Parsons that are

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1152-492: A high power of the stellar mass, high mass luminous stars have much shorter lifetimes. The most luminous stars are always young stars, no more than a few million years for the most extreme. In the Hertzsprung–Russell diagram , the x-axis represents temperature or spectral type while the y-axis represents luminosity or magnitude. The vast majority of stars are found along the main sequence with blue Class O stars found at

1248-427: A late night flight from New York to Washington. The aircraft encountered an electrical storm during which it was enveloped in a sudden bright and loud electrical discharge (0005 h EST, March 19, 1963). Some seconds after this a glowing sphere a little more than 20 cm [8 inches] in diameter emerged from the pilot's cabin and passed down the aisle of the aircraft approximately 50 cm [20 inches] from me, maintaining

1344-749: A letter from John Howell of the sloop Catherine and Mary : As we were coming thro' the Gulf of Florida on 29th of August, a large ball of fire fell from the Element and split our mast in Ten Thousand Pieces, if it were possible; split our Main Beam, also Three Planks of the Side, Under Water, and Three of the Deck; killed one man, another had his Hand carried of [ sic ], and had it not been for

1440-459: A microwave.) Experiments by Eli Jerby and Vladimir Dikhtyar in Israel revealed that microwave plasma balls are made up of nanoparticles with an average radius of 25  nm (9.8 × 10 inches). The team demonstrated the phenomenon with copper, salts, water and carbon. Experiments in 2007 involved shocking silicon wafers with electricity, which vaporizes the silicon and induces oxidation in

1536-446: A natural vortex (e.g., the ' Hill's spherical vortex '). Oleg Meshcheryakov suggests that ball lightning is made of composite nano or submicrometer particles—each particle constituting a battery . A surface discharge shorts these batteries, causing a current that forms the ball. His model is described as an aerosol model that explains all the observable properties and processes of ball lightning. Luminosity Luminosity

1632-619: A pandemonium outside the cottage. I felt a very slight shock in the middle of my right hand, which was closer to the globe than any other part of my body. Jennison, of the Electronics Laboratory at the University of Kent , described his own observation of ball lightning in an article published in Nature in 1969: I was seated near the front of the passenger cabin of an all-metal airliner (Eastern Airlines Flight EA 539) on

1728-509: A point source of light of luminosity L {\displaystyle L} that radiates equally in all directions. A hollow sphere centered on the point would have its entire interior surface illuminated. As the radius increases, the surface area will also increase, and the constant luminosity has more surface area to illuminate, leading to a decrease in observed brightness. F = L A , {\displaystyle F={\frac {L}{A}},} where The surface area of

1824-435: A severe storm. Witnesses described an 8-foot (2.4 m) ball of fire striking and entering the church, nearly destroying it. Large stones from the church walls were hurled onto the ground and through large wooden beams. The ball of fire allegedly smashed the pews and many windows, and filled the church with a foul sulphurous odour and dark, thick smoke. The ball of fire reportedly divided into two segments, one exiting through

1920-433: A soucouyant, it is believed one should heap rice around their house or at the village crossroads; the creature will be obligated to gather the rice, grain by grain, and be caught in the act. To destroy one, coarse salt must be placed in the mortar with the stripped-off skin so that she perishes, unable to put it back on. The skin of the soucouyant is considered valuable and is part of black magic rituals. Belief in soucouyants

2016-400: A sphere with radius r is A = 4 π r 2 {\displaystyle A=4\pi r^{2}} , so for stars and other point sources of light: F = L 4 π r 2 , {\displaystyle F={\frac {L}{4\pi r^{2}}}\,,} where r {\displaystyle r} is the distance from the observer to

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2112-657: A spinning fiery sphere and then having some horizontal motion is very similar to historic and contemporary descriptions of ball lightning   ... It is fascinating to see how closely Gervase's 12th century description matches modern reports of ball lightning. One early account reports on the Great Thunderstorm at a church in Widecombe-in-the-Moor , Devon, in England, on 21 October 1638. Four people died and approximately 60 suffered injuries during

2208-568: A star independent of distance. The concept of magnitude, on the other hand, incorporates distance. The apparent magnitude is a measure of the diminishing flux of light as a result of distance according to the inverse-square law . The Pogson logarithmic scale is used to measure both apparent and absolute magnitudes, the latter corresponding to the brightness of a star or other celestial body as seen if it would be located at an interstellar distance of 10 parsecs (3.1 × 10 metres ). In addition to this brightness decrease from increased distance, there

2304-406: A superconducting phase in a ball lightning. The idea of the superconductivity in a ball lightning was considered earlier. The possibility of the existence of a ball lightning with a composite core was also discussed in this model. One theory that may account for the wide spectrum of observational evidence is the idea of combustion inside the low-velocity region of spherical vortex breakdown of

2400-436: A video at high frame rate. Nevertheless, scientific data on ball lightning remain scarce. Although laboratory experiments have produced effects that are visually similar to reports of ball lightning, how these relate to the supposed phenomenon remains unclear. Descriptions of ball lightning vary widely. It has been described as moving up and down, sideways or in unpredictable trajectories, hovering and moving with or against

2496-411: A white substance that grew into a spherical shape under the cloud, from which a fiery globe fell towards the river. Physicist Emeritus Professor Brian Tanner and historian Giles Gasper of Durham University identified the chronicle entry as probably describing ball lightning, and noted its similarity to other accounts: Gervase's description of a white substance coming out of the dark cloud, falling as

2592-421: A window by smashing it open, the other disappearing somewhere inside the church. Because of the fire and sulphur smell, contemporaries explained the ball of fire as "the devil" or as the "flames of hell". Later, some blamed the entire incident on two people who had been playing cards in the pews during the sermon, thereby incurring God's wrath. In December 1726, a number of British newspapers printed an extract of

2688-458: Is a detached St. Elmo's fire (1964–1970). St. Elmo's fire arises when a sharp conductor, such as a ship's mast, amplifies the atmospheric electric field to breakdown. For a globe the amplification factor is 3. A free ball of ionized air can amplify the ambient field this much by its own conductivity. When this maintains the ionization, the ball is then a soliton in the flow of atmospheric electricity. Powell's kinetic theory calculation found that

2784-409: Is a glow discharge driven by microwave radiation that is guided to the ball along lines of ionized air from lightning clouds where it is produced. The ball serves as a resonant microwave cavity, automatically adjusting its radius to the wavelength of the microwave radiation so that resonance is maintained. The Handel Maser-Soliton theory of ball lightning hypothesizes that the energy source generating

2880-446: Is an absolute measure of radiated electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy , luminosity is the total amount of electromagnetic energy emitted per unit of time by a star , galaxy , or other astronomical objects . In SI units, luminosity is measured in joules per second, or watts . In astronomy, values for luminosity are often given in

2976-526: Is an extra decrease of brightness due to extinction from intervening interstellar dust. By measuring the width of certain absorption lines in the stellar spectrum , it is often possible to assign a certain luminosity class to a star without knowing its distance. Thus a fair measure of its absolute magnitude can be determined without knowing its distance nor the interstellar extinction. In measuring star brightnesses, absolute magnitude, apparent magnitude, and distance are interrelated parameters—if two are known,

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3072-404: Is any relation. Nikola Tesla reportedly could artificially produce 1.5-inch (3.8 cm) balls and conducted some demonstrations of his ability. Tesla was more interested in higher voltages and powers as well as remote transmission of power; the balls he made were just a curiosity. The International Committee on Ball Lightning (ICBL) held regular symposia on the subject. A related group uses

3168-512: Is at present no widely accepted explanation for ball lightning. Several hypotheses have been advanced since the phenomenon was brought into the scientific realm by the English physician and electrical researcher William Snow Harris in 1843, and French Academy scientist François Arago in 1855. This hypothesis suggests that ball lightning consists of vaporized silicon burning through oxidation . Lightning striking Earth's soil could vaporize

3264-481: Is far from being very rapid – they have even been observed occasionally to pause in their course, but they are not the less destructive for all that. A ball of lightning which entered the church of Stralsund, on exploding, projected a number of balls which exploded in their turn like shells. Nicholas II , the final tsar of the Russian Empire, reported witnessing a fiery ball as a child attending church in

3360-457: Is generally used to refer to an object's apparent brightness: that is, how bright an object appears to an observer. Apparent brightness depends on both the luminosity of the object and the distance between the object and observer, and also on any absorption of light along the path from object to observer. Apparent magnitude is a logarithmic measure of apparent brightness. The distance determined by luminosity measures can be somewhat ambiguous, and

3456-635: Is likely the origin of the Soucouyant as well as the Bahamian "Hag" have a strong connection to the Aje, or the witch of the Yoruba people. The Hag, which is similar to the Soucouyant, is very similar to the traditional definition of the Aje. Many Bahamians who descended from the Yoruba referred to old Congolese women as witches who shed their skins in the night and sucked human blood. This have many parallels to

3552-439: Is often erroneously identified as St. Elmo's fire . They are separate and distinct phenomena. The balls have been reported to disperse in many different ways, such as suddenly vanishing, gradually dissipating, being absorbed into an object, "popping," exploding loudly, or even exploding with force, which is sometimes reported as damaging. Accounts also vary on their alleged danger to humans, from lethal to harmless. A review of

3648-541: Is situated the dynamos and electrical apparatus of perhaps the finest electrical plant of its size in the state. There was probably a visiting delegation from the clouds, to the captives of the dynamos on last Monday night, and they certainly had a fine visit and a roystering game of romp. In January 2014, scientists from Northwest Normal University in Lanzhou , China , published the results of recordings made in July 2012 of

3744-533: Is still preserved to an extent in Guyana, Suriname and some Caribbean islands, including Saint Lucia, Dominica, Haïti and Trinidad. Many Caribbean islands have plays about the soucouyant and many other folklore characters. Some of these include Trinidad, Grenada and Barbados. Soucouyants belong to a class of spirits called jumbies. Some believe that soucouyants were brought to the Caribbean from European countries in

3840-447: Is the luminosity in W Hz , S obs is the observed flux density in W m Hz , D L is the luminosity distance in metres, z is the redshift, α is the spectral index (in the sense I ∝ ν α {\displaystyle I\propto {\nu }^{\alpha }} , and in radio astronomy, assuming thermal emission the spectral index is typically equal to 2. ) For example, consider

3936-484: Is thus sometimes called the luminosity distance . When not qualified, the term "luminosity" means bolometric luminosity, which is measured either in the SI units, watts , or in terms of solar luminosities ( L ☉ ). A bolometer is the instrument used to measure radiant energy over a wide band by absorption and measurement of heating. A star also radiates neutrinos , which carry off some energy (about 2% in

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4032-463: Is to derive accurate measurements for each of these components, without which an accurate luminosity figure remains elusive. Extinction can only be measured directly if the actual and observed luminosities are both known, but it can be estimated from the observed colour of a star, using models of the expected level of reddening from the interstellar medium. In the current system of stellar classification , stars are grouped according to temperature, with

4128-462: Is to measure the star's apparent brightness and distance. A third component needed to derive the luminosity is the degree of interstellar extinction that is present, a condition that usually arises because of gas and dust present in the interstellar medium (ISM), the Earth's atmosphere , and circumstellar matter . Consequently, one of astronomy's central challenges in determining a star's luminosity

4224-511: Is to set the bandwidth to the observing frequency, which effectively assumes the power radiated has uniform intensity from zero frequency up to the observing frequency. In the case above, the total power is 4×10 × 1.4×10 = 5.7×10 W . This is sometimes expressed in terms of the total (i.e. integrated over all wavelengths) luminosity of the Sun which is 3.86×10 W , giving a radio power of 1.5×10 L ⊙ . The Stefan–Boltzmann equation applied to

4320-504: The Max Planck Institute , have reportedly produced a ball lightning-type effect by discharging a high-voltage capacitor in a tank of water. Many modern experiments involve using a microwave oven to produce small rising glowing balls, often referred to as plasma balls . Generally, the experiments are conducted by placing a lit or recently extinguished match or other small object in a microwave oven. The burnt portion of

4416-486: The Bahamian Hag and Yoruba was made during the 19th century by Alfred Burdon Ellis in his book about the Yoruba published in 1894. But he associated it with the Yoruba spirit of nightmare, known as Shigidi. In Divining the self , Velma E Love describes the Aje as "a blood-sucking, wicked, dreadful cannibal who transforms herself into a bird at night and flies to distant places, to hold nocturnal meetings with her fellow witches." The Bahamian Hag as described by Clavel: "when

4512-516: The British ship HMS Warren Hastings . The crew watched one ball descend, killing a man on deck and setting the main mast on fire. A crewman went out to retrieve the fallen body and was struck by a second ball, which knocked him back and left him with mild burns. A third man was killed by contact with the third ball. Crew members reported a persistent, sickening sulphur smell afterward. Ebenezer Cobham Brewer , in his 1864 US edition of A Guide to

4608-656: The Scientific Knowledge of Things Familiar , discusses "globular lightning". He describes it as slow-moving balls of fire or explosive gas that sometimes fall to the earth or run along the ground during a thunderstorm. He said that the balls sometimes split into smaller balls and may explode "like a cannon ". In his book Thunder and Lightning , translated into English in 1875, French science-writer Wilfrid de Fonvielle wrote that there had been about 150 reports of globular lightning: Globular lightning seems to be particularly attracted to metals; thus it will seek

4704-510: The Yoruba Aje with a few differences. Among the Yoruba, the Aje leaves her body and turns into an animal, but the Hag sheds her skin and turns into a ball of fire. Both the Hag and the Aje are associated with old women, leaving their bodies behind and sucking blood. Items of Folk-lore from Bahama Negroes , written by Clavel and published in 1904, describes the Bahamian version. The parallels of

4800-572: The absolute magnitude scale is actually defined as a fixed luminosity of 3.0128 × 10  W . Therefore, the absolute magnitude can be calculated from a luminosity in watts: M b o l = − 2.5 log 10 ⁡ L ∗ L 0 ≈ − 2.5 log 10 ⁡ L ∗ + 71.1974 {\displaystyle M_{\mathrm {bol} }=-2.5\log _{10}{\frac {L_{*}}{L_{0}}}\approx -2.5\log _{10}L_{*}+71.1974} where L 0

4896-442: The after-glow comes mostly from metastable NO ions, which are long-lived at low temperatures. It occurred in air and in nitrous oxide, which possess such metastable ions, and not in atmospheres of argon, carbon dioxide, or helium, which do not. The soliton model of a ball lightning was further developed. It was suggested that a ball lightning is based on spherically symmetric nonlinear oscillations of charged particles in plasma –

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4992-449: The analogue of a spatial Langmuir soliton. These oscillations were described in both classical and quantum approaches. It was found that the most intense plasma oscillations occur in the central regions of a ball lightning. It is suggested that bound states of radially oscillating charged particles with oppositely oriented spins – the analogue of Cooper pairs – can appear inside a ball lightning. This phenomenon, in its turn, can lead to

5088-694: The available literature published in 1972 identified the properties of a "typical" ball lightning, whilst cautioning against over-reliance on eye-witness accounts: Ball lightning is a possible source of legends that describe luminous balls, such as the mythological Anchimayen from Argentinean and Chilean Mapuche culture. According to a statistical investigation carried out in 1960, of 1,962 Oak Ridge National Laboratory monthly role personnel, and of all 15,923 Union Carbide Nuclear Company personnel in Oak Ridge, found 5.6% and 3.1% respectively reported seeing ball lightning. A Scientific American article summarized

5184-472: The ball lightning is a large (several cubic kilometers) atmospheric maser . The ball lightning appears as a plasma caviton at the antinodal plane of the microwave radiation from the maser. In 2017, Researchers from Zhejiang University in Hangzhou, China, proposed that the bright glow of lightning balls is created when microwaves become trapped inside a plasma bubble. At the tip of a lightning stroke reaching

5280-416: The ball size is set by the second Townsend coefficient (the mean free path of conduction electrons) near breakdown. Wandering glow discharges are found to occur within certain industrial microwave ovens and continue to glow for several seconds after power is shut off. Arcs drawn from high-power low-voltage microwave generators also are found to exhibit afterglow. Powell measured their spectra, and found that

5376-500: The case of the Sun), contributing to the star's total luminosity. The IAU has defined a nominal solar luminosity of 3.828 × 10  W to promote publication of consistent and comparable values in units of the solar luminosity. While bolometers do exist, they cannot be used to measure even the apparent brightness of a star because they are insufficiently sensitive across the electromagnetic spectrum and because most wavelengths do not reach

5472-470: The company of his grandfather Alexander II . Once my parents were away, and I was at the all-night vigil with my grandfather in the small church in Alexandria . During the service there was a powerful thunderstorm, streaks of lightning flashed one after the other, and it seemed as if the peals of thunder would shake even the church and the whole world to its foundations. Suddenly it became quite dark,

5568-455: The core is surrounded by a thin electron layer with a charge nearly equal in magnitude to that of the core. A vacuum exists between the core and the electron layer containing an intense electromagnetic (EM) field , which is reflected and guided by the electron layer. The microwave EM field applies a ponderomotive force (radiation pressure) to the electrons preventing them from falling into the core. Pyotr Kapitsa proposed that ball lightning

5664-645: The electromagnetic field of the 50 Hz high-voltage power transmission line in the vicinity, were observed. From the spectrum, the temperature of the ball lightning was assessed as being lower than the temperature of the parent lightning (<15,000 to 30,000 K). The observed data are consistent with vaporization of soil as well as with ball lightning's sensitivity to electric fields . Scientists have long attempted to produce ball lightning in laboratory experiments. While some experiments have produced effects that are visually similar to reports of natural ball lightning, it has not yet been determined whether there

5760-451: The experiment was under way, ball lightning appeared, travelled down the string, struck Richmann's forehead and killed him. The ball had left a red spot on Richmann's forehead, his shoes were blown open, and his clothing was singed. His engraver was knocked unconscious. The door-frame of the room was split and the door was torn from its hinges. An English journal reported that during an 1809 storm, three "balls of fire" appeared and "attacked"

5856-539: The explosion, the ball seemed to be the size of a large mill-stone. A 1753 report recounts lethal ball lightning when professor Georg Richmann of Saint Petersburg , Russia, constructed a kite-flying apparatus similar to Benjamin Franklin 's proposal a year earlier. Richmann was attending a meeting of the Academy of Sciences when he heard thunder and ran home with his engraver to capture the event for posterity. While

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5952-438: The first ever recorded spectra of natural ball lightning were published. The theorized forms of silicon storage in soil include nanoparticles of Si, SiO , and SiC . Matthew Francis has dubbed this the "dirt clod hypothesis", in which the spectrum of ball lightning shows that it shares chemistry with soil. In this model ball lightning is assumed to have a solid, positively charged core. According to this underlying assumption,

6048-588: The form of French vampire-myths. These beliefs intermingled with those of enslaved Africans. In the French West Indies , specifically the islands of Guadeloupe and Martinique, and also in Suriname, the Soukougnan or Soukounian is a person able to shed his or her skin to turn into a vampiric fireball. In general, these figures can be of any gender and age. The term "Loogaroo" also used to describe

6144-513: The generic name "Unconventional Plasmas". The last ICBL symposium was tentatively scheduled for July 2012 in San Marcos, Texas but was cancelled due to a lack of submitted abstracts. Ohtsuki and Ofuruton described producing "plasma fireballs" by microwave interference within an air-filled cylindrical cavity fed by a rectangular waveguide using a 2.45 GHz, 5 kW (maximum power) microwave oscillator. Some scientific groups, including

6240-426: The ground, a relativistic electron bunch can be produced when in contact with microwave radiation. The latter ionizes the local air and the radiation pressure evacuates the resulting plasma, forming a spherical plasma bubble that stably traps the radiation. Microwaves trapped inside the ball continue to generate plasma for a moment to maintain the bright flashes described in observer accounts. The ball eventually fades as

6336-415: The infrared. Bolometric luminosities can also be calculated using a bolometric correction to a luminosity in a particular passband. The term luminosity is also used in relation to particular passbands such as a visual luminosity of K-band luminosity. These are not generally luminosities in the strict sense of an absolute measure of radiated power, but absolute magnitudes defined for a given filter in

6432-424: The latter is represented in kelvins , but in most cases neither can be measured directly. To determine a star's radius, two other metrics are needed: the star's angular diameter and its distance from Earth. Both can be measured with great accuracy in certain cases, with cool supergiants often having large angular diameters, and some cool evolved stars having masers in their atmospheres that can be used to measure

6528-410: The light source. For stars on the main sequence , luminosity is also related to mass approximately as below: L L ⊙ ≈ ( M M ⊙ ) 3.5 . {\displaystyle {\frac {L}{L_{\odot }}}\approx {\left({\frac {M}{M_{\odot }}}\right)}^{3.5}.} Luminosity is an intrinsic measurable property of

6624-415: The main sequence and they are called giants or supergiants. Blue and white supergiants are high luminosity stars somewhat cooler than the most luminous main sequence stars. A star like Deneb , for example, has a luminosity around 200,000 L ⊙ , a spectral type of A2, and an effective temperature around 8,500 K, meaning it has a radius around 203  R ☉ (1.41 × 10   m ). For comparison,

6720-464: The main tack, they observed the ball rise almost perpendicularly, and not above forty or fifty yards [35 or 45 m] from the main chains when it went off with an explosion, as great as if a hundred cannons had been discharged at the same time, leaving behind it a strong sulphurous smell. By this explosion the main top-mast was shattered into pieces and the main mast went down to the keel. Five men were knocked down and one of them very bruised. Just before

6816-412: The massive, very young and energetic Class O stars boasting temperatures in excess of 30,000  K while the less massive, typically older Class M stars exhibit temperatures less than 3,500 K. Because luminosity is proportional to temperature to the fourth power, the large variation in stellar temperatures produces an even vaster variation in stellar luminosity. Because the luminosity depends on

6912-399: The object flares up into a large ball of fire, while "plasma balls" float near the oven chamber ceiling. Some experiments describe covering the match with an inverted glass jar, which contains both the flame and the balls so that they do not damage the chamber walls. (A glass jar, however, eventually explodes rather than simply causing charred paint or melting metal, as happens to the inside of

7008-711: The observed visible brightness from Earth which depends on the distance of the object. The absolute magnitude is the apparent magnitude at a distance of 10  pc (3.1 × 10   m ), therefore the bolometric absolute magnitude is a logarithmic measure of the bolometric luminosity. The difference in bolometric magnitude between two objects is related to their luminosity ratio according to: M bol1 − M bol2 = − 2.5 log 10 ⁡ L 1 L 2 {\displaystyle M_{\text{bol1}}-M_{\text{bol2}}=-2.5\log _{10}{\frac {L_{\text{1}}}{L_{\text{2}}}}} where: The zero point of

7104-479: The optical spectrum of what was thought to be natural ball lightning made by chance during the study of ordinary cloud–ground lightning on the Tibetan Plateau . At a distance of 900 m (3,000 ft), a total of 1.64 seconds of digital video of the ball lightning and its spectrum was made, from the formation of the ball lightning after the ordinary lightning struck the ground, up to the optical decay of

7200-424: The parallax using VLBI . However, for most stars the angular diameter or parallax, or both, are far below our ability to measure with any certainty. Since the effective temperature is merely a number that represents the temperature of a black body that would reproduce the luminosity, it obviously cannot be measured directly, but it can be estimated from the spectrum. An alternative way to measure stellar luminosity

7296-414: The phenomenon. Additional video was recorded by a high-speed (3000 frames/sec) camera, which captured only the last 0.78 seconds of the event, due to its limited recording capacity. Both cameras were equipped with slitless spectrographs . The researchers detected emission lines of neutral atomic silicon , calcium , iron , nitrogen , and oxygen —in contrast with mainly ionized nitrogen emission lines in

7392-461: The radiation held within the bubble starts to decay and microwaves are discharged from the sphere. The lightning balls can dramatically explode as the structure destabilizes. The theory could explain many of the strange characteristics of ball lightning. For instance, microwaves are able to pass through glass, which helps to explain why balls could be formed indoors. Julio Rubinstein, David Finkelstein , and James R. Powell proposed that ball lightning

7488-588: The railings of balconies, or else water or gas pipes etc., It has no peculiar tint of its own but will appear of any colour as the case may be ... at Coethen in the Duchy of Anhalt it appeared green. M. Colon, Vice-President of the Geological Society of Paris, saw a ball of lightning descend slowly from the sky along the bark of a poplar tree; as soon as it touched the earth it bounced up again, and disappeared without exploding. On 10th of September 1845

7584-426: The red supergiant Betelgeuse has a luminosity around 100,000 L ⊙ , a spectral type of M2, and a temperature around 3,500 K, meaning its radius is about 1,000  R ☉ (7.0 × 10   m ). Red supergiants are the largest type of star, but the most luminous are much smaller and hotter, with temperatures up to 50,000 K and more and luminosities of several million L ⊙ , meaning their radii are just

7680-450: The same as the 1904 version of Clavel, but the Hags can also be men. Ball lightning Ball lightning is a rare and unexplained phenomenon described as luminescent , spherical objects that vary from pea-sized to several meters in diameter. Though usually associated with thunderstorms , the observed phenomenon is reported to last considerably longer than the split-second flash of

7776-480: The same height and course for the whole distance over which it could be observed. A beautiful yet strange phenomenon was seen in this city on last Monday night. The wind was high and the air seemed to be full of electricity. In front of, above and around the new Hall of Engineering of the School of Mines , balls of fire played tag for half an hour, to the wonder and amazement of all who saw the display. In this building

7872-599: The silica contained within it, and somehow separate the oxygen from the silicon dioxide, turning it into pure silicon vapor. As it cools, the silicon could condense into a floating aerosol, bound by its charge, glowing due to the heat of silicon recombining with oxygen . An experimental investigation of this effect, published in 2007, reported producing "luminous balls with lifetime in the order of seconds" by evaporating pure silicon with an electric arc. Videos and spectrographs of this experiment have been made available. This hypothesis got significant supportive data in 2014, when

7968-650: The soucouyant, possibly comes from the French word for werewolf: Loup-garou ; often confused with each other since they are pronounced the same. In Haiti, what would be considered a werewolf , is called jé-rouges ("red eyes"). As in Haiti, the Loogaroo is also common in Mauritian culture . With the passage of time and gradual changes in the story, the soucouyant is no longer exclusively described as an elderly woman. It

8064-591: The spectral index α of the source, and a relativistic correction must be made for the fact that the frequency scale in the emitted rest frame is different from that in the observer's rest frame . So the full expression for radio luminosity, assuming isotropic emission, is L ν = S o b s 4 π D L 2 ( 1 + z ) 1 + α {\displaystyle L_{\nu }={\frac {S_{\mathrm {obs} }4\pi {D_{L}}^{2}}{(1+z)^{1+\alpha }}}} where L ν

8160-411: The spectrum of the parent lightning. The ball lightning traveled horizontally across the video frame at an average speed equivalent of 8.6 m/s (28 ft/s). It had a diameter of 5 m (16 ft) and covered a distance of about 15 m (49 ft) within those 1.64 s. Oscillations in the light intensity and in the oxygen and nitrogen emission at a frequency of 100 hertz , possibly caused by

8256-468: The study as having found that ball lightning had been seen by 5% of the population of the Earth. Another study analyzed reports of more than 2,000 cases. The chronicle of Gervase of Canterbury , an English monk, contains what is possibly the earliest known reference to ball lightning, dated 7 June 1195. He states, "A marvellous sign descended near London", consisting of a dense and dark cloud, emitting

8352-414: The surface of the Earth. In practice bolometric magnitudes are measured by taking measurements at certain wavelengths and constructing a model of the total spectrum that is most likely to match those measurements. In some cases, the process of estimation is extreme, with luminosities being calculated when less than 1% of the energy output is observed, for example with a hot Wolf-Rayet star observed only in

8448-478: The terms of the luminosity of the Sun , L ⊙ . Luminosity can also be given in terms of the astronomical magnitude system: the absolute bolometric magnitude ( M bol ) of an object is a logarithmic measure of its total energy emission rate, while absolute magnitude is a logarithmic measure of the luminosity within some specific wavelength range or filter band . In contrast, the term brightness in astronomy

8544-449: The third can be determined. Since the Sun's luminosity is the standard, comparing these parameters with the Sun's apparent magnitude and distance is the easiest way to remember how to convert between them, although officially, zero point values are defined by the IAU. The magnitude of a star, a unitless measure, is a logarithmic scale of observed visible brightness. The apparent magnitude is

8640-403: The top left of the chart while red Class M stars fall to the bottom right. Certain stars like Deneb and Betelgeuse are found above and to the right of the main sequence, more luminous or cooler than their equivalents on the main sequence. Increased luminosity at the same temperature, or alternatively cooler temperature at the same luminosity, indicates that these stars are larger than those on

8736-514: The vapors. The visual effect can be described as small glowing, sparkling orbs that roll around a surface. Two Brazilian scientists, Antonio Pavão and Gerson Paiva of the Federal University of Pernambuco have reportedly consistently made small long-lasting balls using this method. These experiments stemmed from the theory that ball lightning is actually oxidized silicon vapors (see vaporized silicon hypothesis , below) . There

8832-419: The victim sleeps, leaving black and blue marks on the body in the morning. If the soucouyant draws too much blood, it is believed that the victim will either die and become a soucouyant or perish entirely, leaving the killer to assume their skin. The soucouyant practices black magic . Soucouyants trade their victims' blood for evil powers with Bazil , the demon who resides in the silk cotton tree . To expose

8928-508: The violent rains, our Sails would have been of a Blast of Fire. One particularly large example was reported "on the authority of Dr. Gregory" in 1749: Admiral Chambers on board the Montague , 4 November 1749, was taking an observation just before noon...he observed a large ball of blue fire about three miles [5 km] distant from them. They immediately lowered their topsails, but it came up so fast upon them, that, before they could raise

9024-643: The wind; attracted to, unaffected by, or repelled from buildings, people, cars and other objects. Some accounts describe it as moving through solid masses of wood or metal without effect, while others describe it as destructive and melting or burning those substances. Its appearance has also been linked to power lines , altitudes of 300 m (1,000 feet) and higher, and during thunderstorms and calm weather. Ball lightning has been described as transparent , translucent , multicolored, evenly lit, radiating flames, filaments or sparks, with shapes that vary between spheres, ovals, tear-drops, rods, or disks. Ball lightning

9120-439: Was completely calm. He crossed himself just as calmly as he had when the fiery ball had flown near us, and I felt that it was unseemly and not courageous to be frightened as I was. I felt that one had only to look at what was happening and believe in the mercy of God, as he, my grandfather, did. After the ball had passed through the whole church, and suddenly gone out through the door, I again looked at my grandfather. A faint smile

9216-502: Was on his face, and he nodded his head at me. My panic disappeared, and from that time I had no more fear of storms. British occultist Aleister Crowley reported witnessing what he referred to as "globular electricity" during a thunderstorm on Lake Pasquaney in New Hampshire , United States, in 1916. He was sheltered in a small cottage when he, in his own words, ...noticed, with what I can only describe as calm amazement, that

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