British Astronomical Association
The British Astronomical Association was formed in 1890 as a national body to support the UK's amateur astronomers. Throughout its history, the BAA has encouraged observers to make scientifically valuable observations in collaboration with professional colleagues. Among the BAA's first presidents was Walter Maunder, discoverer of the seventeenth century dearth in sunspots now known as the Maunder Minimum which he achieved by analysing historical observations; this spirit of observing the night sky scientifically was championed by George Alcock, who discovered five comets and five novae using nothing more than a pair of binoculars. The BAA continues to contribute to the science of astronomy despite modern competition from space-based telescopes and automated professional observatories. Modern digital sensors, coupled with techniques such as lucky imaging, mean that modest amateur equipment can rival what professional observatories could have achieved a few decades ago; the vastness of the night sky, together with the sheer number of amateur observatories, mean that BAA members are the first to pick up new phenomena.
In recent years, the Association's leading supernova hunter, Tom Boles, has discovered over 150 supernovae. He now holds the world record for the greatest number of such events discovered by any individual in history. More the BAA has worked with international partners. Modern communications allow astronomers in different timezones around the world to hand over the monitoring of variable stars and planetary weather systems to colleagues on other continents as the Sun comes up, resulting in a 24-hour watch on the sky. For example, the Association's Variable Star Section works with the American Association of Variable Star Observers, meanwhile its Jupiter Section works with a global network of planetary observers through the JUPOS collaboration; the Association's longest standing publication is its Journal, published six times a year and sent to all members. Once a year, the Association publishes a Handbook which comprises an almanac for the following year. Electronic bulletins are issued to give more immediate notice by email of discoveries, astronomical news and BAA meetings.
The Association operates a wide range of observing Sections which specialise in particular branches of astronomy, welcoming observers and astronomy enthusiasts of all abilities in a spirit of collaboration and mutual help. It founded and supports the Campaign for Dark Skies, a UK-wide campaign against excessive light pollution; the BAA leases office space from the Royal Astronomical Society, in Burlington House, London. Many of its meetings are held there. In October 1890, the BAA was formed to support amateur astronomers in the UK. In many ways it is a counterpart to the Royal Astronomical Society - which supports professional observers - and the two organisations have long shared the same premises; the idea for this organisation was first publicly proposed by Irish astronomer William H. S. Monck in a letter published in The English Mechanic on July 12. Playing a significant role in the founding of the Association was English astronomer E. Walter Maunder, with the help of his brother Frid Maunder and William H. Maw.
The first meeting of the Association was held on 1890 October 24, with 60 of the initial 283 members in attendance. It was decided to run the association with a provisional 48-member Council that included four women: Margaret Huggins, Elizabeth Brown, Agnes Clerke and Agnes Giberne; the society formed several observing Sections for specialised topics in astronomy. Elizabeth Brown the only woman in England at the time to own her own observatory, became head of the Solar Section; the Association was presented with or bequeathed various astronomical instruments, but lacked the funds to build their own observatory. A total of 477 instruments were acquired during the first 117 years since the Association was founded; the Association held monthly meetings in London, but established branches to cater for members who could not attend London activities and desired to meet in their own areas. The first of these was the Northwestern Branch which served members in the Northwest of England, centred on Manchester.
The Branch was formed in 1892, in 1903 it ceded from the BAA to form the Manchester Astronomical Society. North Western Branch Presidents S. O. Kell 1892-1895 Prof. T. H. Core 1895-1903In 1891, a group of amateurs in Australia began discussing the idea of setting up branches of the BAA in their own country. What would become the New South Wales Branch was established in 1895 and would be the only one to survive for more than a brief period; this branch is still in existence. New South Wales Branch Presidents John Tebbutt 1894-1896 George Handley Knibbs 1896-1898 Rev. Thomas Roseby 1898-1900 Walter Frederick Gale 1900-1902 William John MacDonnell 1902-1904 George Denton Hirst 1904-1906 Charles J. Merfield 1906-1907 Hugh Wright 1907-1909 James Nangle 1909-1911 Rev. Thomas Roseby 1911-1914 Walter Frederick Gale 1914-1923 Rev. Edward F. Pigot 1923-1925 J. J. Richardson 1925-1927 Walter Frederick Gale 1927-1929 James Nangle 1929-1930 Walter Frederick Gale 1930-1932 & 1932-1933 Rev. William O'Leary 1933-1934 & 1934-1935 Walter Frederick Gale 1935-1936 Alan Patrick Mackerras 1936-1937 Walter Frederick Gale 1937-1938 & 1938-1939 Henry Herbert Baker 1939-1940 Harley Weston Wood 1940-1942 Walter Frederick Gale 1942-1943 Alan Patrick Mackerras 1943-1945 Horace Edgar Frank Pinnock 1945-1946 Alan Patrick Mackerras 1946-1947 W. H. Robertson 1947-1950 D. Coleman-Trainor 1950-1951 Alan Patrick Mackerras 1951-1954 Harley Weston Wood 1954-1956 Rev. Thomas Noël Burke-Gaffney 1956-1958 W. Kemp Robertso
Auriga is one of the 88 modern constellations. Located north of the celestial equator, its name is the Latin word for “the charioteer”, associating it with various mythological beings, including Erichthonius and Myrtilus. Auriga is most prominent during winter evenings in the northern Hemisphere, along with the five other constellations that have stars in the Winter Hexagon asterism; because of its northern declination, Auriga is only visible in its entirety as far as 34° south. A large constellation, with an area of 657 square degrees, it is half the size of the largest constellation, Hydra, its brightest star, Capella, is an unusual multiple star system among the brightest stars in the night sky. Beta Aurigae is an interesting variable star in the constellation; because of its position near the winter Milky Way, Auriga has many bright open clusters in its borders, including M36, M37, M38, popular targets for amateur astronomers. In addition, it has one prominent nebula, the Flaming Star Nebula, associated with the variable star AE Aurigae.
In Chinese mythology, Auriga's stars were incorporated into several constellations, including the celestial emperors' chariots, made up of the modern constellation's brightest stars. Auriga is home to the radiant for the Aurigids, Zeta Aurigids, Delta Aurigids, the hypothesized Iota Aurigids; the first record of Auriga's stars was in Mesopotamia as a constellation called GAM, representing a scimitar or crook. However, this may have represented just the modern constellation as a whole. GAM in the MUL. APIN; the crook of Auriga shepherd. It was formed from most of the stars of the modern constellation. Bedouin astronomers created constellations that were groups of animals, where each star represented one animal; the stars of Auriga comprised a herd of goats, an association present in Greek mythology. The association with goats carried into the Greek astronomical tradition, though it became associated with a charioteer along with the shepherd. In Greek mythology, Auriga is identified as the mythological Greek hero Erichthonius of Athens, the chthonic son of Hephaestus, raised by the goddess Athena.
Erichthonius was credited to be the inventor of the quadriga, the four-horse chariot, which he used in the battle against the usurper Amphictyon, the event that made Erichthonius the king of Athens. His chariot was created in the image of the Sun's chariot, the reason Zeus placed him in the heavens; the Athenian hero dedicated himself to Athena and, soon after, Zeus raised him into the night sky in honor of his ingenuity and heroic deeds. Auriga, however, is sometimes described as Myrtilus, Hermes's son and the charioteer of Oenomaus; the association of Auriga and Myrtilus is supported by depictions of the constellation, which show a chariot. Myrtilus's chariot was destroyed in a race intended for suitors to win the heart of Oenomaus's daughter Hippodamia. Myrtilus earned his position in the sky when Hippodamia's successful suitor, killed him, despite his complicity in helping Pelops win her hand. After his death, Myrtilus's father Hermes placed him in the sky, yet another mythological association of Auriga is Theseus's son Hippolytus.
He was ejected from Athens after he refused the romantic advances of his stepmother Phaedra, who committed suicide as a result. He was revived by Asclepius. Regardless of Auriga's specific representation, it is that the constellation was created by the ancient Greeks to commemorate the importance of the chariot in their society. An incidental appearance of Auriga in Greek mythology is as the limbs of Medea's brother. In the myth of Jason and the Argonauts, as they journeyed home, Medea killed her brother and dismembered him, flinging the parts of his body into the sea, represented by the Milky Way; each individual star represents a different limb. Capella is associated with the mythological she-goat Amalthea, it forms an asterism with the stars Epsilon Aurigae, Zeta Aurigae, Eta Aurigae, the latter two of which are known as the Haedi. Though most associated with Amalthea, Capella has sometimes been associated with Amalthea's owner, a nymph; the myth of the nymph says that the goat's hideous appearance, resembling a Gorgon, was responsible for the Titans' defeat, because Zeus skinned the goat and wore it as his aegis.
The asterism containing the three goats had been a separate constellation. Before that, Capella was sometimes seen as its own constellation—by Pliny the Elder and Manilius—called Capra, Caper, or Hircus, all of which relate to its status as the "goat star". Zeta Aurigae and Eta Aurigae were first called the "Kids" by Cleostratus, an ancient Greek astronomer. Traditionally, illustrations of Auriga represent it as its driver; the charioteer has two kids under his left arm. However, depictions of Auriga have been inconsistent over the years; the reins in his right hand have been drawn as a whip, though Capella is always over his left shoulder and the Kids under his left arm. The 1488 atlas Hyginus deviated from this typical depiction by showing a four-wheeled cart driven by Auriga
The radial velocity of an object with respect to a given point is the rate of change of the distance between the object and the point. That is, the radial velocity is the component of the object's velocity that points in the direction of the radius connecting the object and the point. In astronomy, the point is taken to be the observer on Earth, so the radial velocity denotes the speed with which the object moves away from or approaches the Earth. In astronomy, radial velocity is measured to the first order of approximation by Doppler spectroscopy; the quantity obtained by this method may be called the barycentric radial-velocity measure or spectroscopic radial velocity. However, due to relativistic and cosmological effects over the great distances that light travels to reach the observer from an astronomical object, this measure cannot be transformed to a geometric radial velocity without additional assumptions about the object and the space between it and the observer. By contrast, astrometric radial velocity is determined by astrometric observations.
Light from an object with a substantial relative radial velocity at emission will be subject to the Doppler effect, so the frequency of the light decreases for objects that were receding and increases for objects that were approaching. The radial velocity of a star or other luminous distant objects can be measured by taking a high-resolution spectrum and comparing the measured wavelengths of known spectral lines to wavelengths from laboratory measurements. A positive radial velocity indicates the distance between the objects was increasing. In many binary stars, the orbital motion causes radial velocity variations of several kilometers per second; as the spectra of these stars vary due to the Doppler effect, they are called spectroscopic binaries. Radial velocity can be used to estimate the ratio of the masses of the stars, some orbital elements, such as eccentricity and semimajor axis; the same method has been used to detect planets around stars, in the way that the movement's measurement determines the planet's orbital period, while the resulting radial-velocity amplitude allows the calculation of the lower bound on a planet's mass using the binary mass function.
Radial velocity methods alone may only reveal a lower bound, since a large planet orbiting at a high angle to the line of sight will perturb its star radially as much as a much smaller planet with an orbital plane on the line of sight. It has been suggested that planets with high eccentricities calculated by this method may in fact be two-planet systems of circular or near-circular resonant orbit; the radial velocity method to detect exoplanets is based on the detection of variations in the velocity of the central star, due to the changing direction of the gravitational pull from an exoplanet as it orbits the star. When the star moves towards us, its spectrum is blueshifted, while it is redshifted when it moves away from us. By looking at the spectrum of a star—and so, measuring its velocity—it can be determined if it moves periodically due to the influence of an exoplanet companion. From the instrumental perspective, velocities are measured relative to the telescope's motion. So an important first step of the data reduction is to remove the contributions of the Earth's elliptic motion around the sun at ± 30 km/s, a monthly rotation of ± 13 m/s of the Earth around the center of gravity of the Earth-Moon system, the daily rotation of the telescope with the Earth crust around the Earth axis, up to ±460 m/s at the equator and proportional to the cosine of the telescope's geographic latitude, small contributions from the Earth polar motion at the level of mm/s, contributions of 230 km/s from the motion around the Galactic center and associated proper motions.
In the case of spectroscopic measurements corrections of the order of ±20 cm/s with respect to aberration. Proper motion Peculiar velocity Relative velocity Space velocity The Radial Velocity Equation in the Search for Exoplanets
The Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics. The kelvin is the base unit of temperature in the International System of Units; until 2018, the kelvin was defined as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. In other words, it was defined such that the triple point of water is 273.16 K. On 16 November 2018, a new definition was adopted, in terms of a fixed value of the Boltzmann constant. For legal metrology purposes, the new definition will come into force on 20 May 2019; the Kelvin scale is named after the Belfast-born, Glasgow University engineer and physicist William Thomson, 1st Baron Kelvin, who wrote of the need for an "absolute thermometric scale". Unlike the degree Fahrenheit and degree Celsius, the kelvin is not referred to or written as a degree; the kelvin is the primary unit of temperature measurement in the physical sciences, but is used in conjunction with the degree Celsius, which has the same magnitude.
The definition implies that absolute zero is equivalent to −273.15 °C. In 1848, William Thomson, made Lord Kelvin, wrote in his paper, On an Absolute Thermometric Scale, of the need for a scale whereby "infinite cold" was the scale's null point, which used the degree Celsius for its unit increment. Kelvin calculated; this absolute scale is known today as the Kelvin thermodynamic temperature scale. Kelvin's value of "−273" was the negative reciprocal of 0.00366—the accepted expansion coefficient of gas per degree Celsius relative to the ice point, giving a remarkable consistency to the accepted value. In 1954, Resolution 3 of the 10th General Conference on Weights and Measures gave the Kelvin scale its modern definition by designating the triple point of water as its second defining point and assigned its temperature to 273.16 kelvins. In 1967/1968, Resolution 3 of the 13th CGPM renamed the unit increment of thermodynamic temperature "kelvin", symbol K, replacing "degree Kelvin", symbol °K. Furthermore, feeling it useful to more explicitly define the magnitude of the unit increment, the 13th CGPM held in Resolution 4 that "The kelvin, unit of thermodynamic temperature, is equal to the fraction 1/273.16 of the thermodynamic temperature of the triple point of water."In 2005, the Comité International des Poids et Mesures, a committee of the CGPM, affirmed that for the purposes of delineating the temperature of the triple point of water, the definition of the Kelvin thermodynamic temperature scale would refer to water having an isotopic composition specified as Vienna Standard Mean Ocean Water.
In 2018, Resolution A of the 26th CGPM adopted a significant redefinition of SI base units which included redefining the Kelvin in terms of a fixed value for the Boltzmann constant of 1.380649×10−23 J/K. When spelled out or spoken, the unit is pluralised using the same grammatical rules as for other SI units such as the volt or ohm; when reference is made to the "Kelvin scale", the word "kelvin"—which is a noun—functions adjectivally to modify the noun "scale" and is capitalized. As with most other SI unit symbols there is a space between the kelvin symbol. Before the 13th CGPM in 1967–1968, the unit kelvin was called a "degree", the same as with the other temperature scales at the time, it was distinguished from the other scales with either the adjective suffix "Kelvin" or with "absolute" and its symbol was °K. The latter term, the unit's official name from 1948 until 1954, was ambiguous since it could be interpreted as referring to the Rankine scale. Before the 13th CGPM, the plural form was "degrees absolute".
The 13th CGPM changed the unit name to "kelvin". The omission of "degree" indicates that it is not relative to an arbitrary reference point like the Celsius and Fahrenheit scales, but rather an absolute unit of measure which can be manipulated algebraically. In science and engineering, degrees Celsius and kelvins are used in the same article, where absolute temperatures are given in degrees Celsius, but temperature intervals are given in kelvins. E.g. "its measured value was 0.01028 °C with an uncertainty of 60 µK." This practice is permissible because the degree Celsius is a special name for the kelvin for use in expressing relative temperatures, the magnitude of the degree Celsius is equal to that of the kelvin. Notwithstanding that the official endorsement provided by Resolution 3 of the 13th CGPM states "a temperature interval may be expressed in degrees Celsius", the practice of using both °C and K is widespread throughout the scientific world; the use of SI prefixed forms of the degree Celsius to express a temperature interval has not been adopted.
In 2005 the CIPM embarked on a programme to redefine the kelvin using a more experimentally rigorous methodology. In particular, the committee proposed redefining the kelvin such that Boltzmann's constant takes the exact value 1.3806505×10−23 J/K. The committee had hoped tha
Asymptotic giant branch
The asymptotic giant branch is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars late in their lives. Observationally, an asymptotic-giant-branch star will appear as a bright red giant with a luminosity ranging up to thousands of times greater than the Sun, its interior structure is characterized by a central and inert core of carbon and oxygen, a shell where helium is undergoing fusion to form carbon, another shell where hydrogen is undergoing fusion forming helium, a large envelope of material of composition similar to main-sequence stars. When a star exhausts the supply of hydrogen by nuclear fusion processes in its core, the core contracts and its temperature increases, causing the outer layers of the star to expand and cool; the star becomes a red giant, following a track towards the upper-right hand corner of the HR diagram. Once the temperature in the core has reached 3×108 K, helium burning begins.
The onset of helium burning in the core halts the star's cooling and increase in luminosity, the star instead moves down and leftwards in the HR diagram. This is the horizontal branch or red clump, or a blue loop for stars more massive than about 2 M☉. After the completion of helium burning in the core, the star again moves to the right and upwards on the diagram and expanding as its luminosity increases, its path is aligned with its previous red-giant track, hence the name asymptotic giant branch, although the star will become more luminous on the AGB than it did at the tip of the red giant branch. Stars at this stage of stellar evolution are known as AGB stars; the AGB phase is divided into two parts, the early AGB and the thermally pulsing AGB. During the E-AGB phase, the main source of energy is helium fusion in a shell around a core consisting of carbon and oxygen. During this phase, the star swells up to giant proportions to become a red giant again; the star's radius may become as large as one astronomical unit.
After the helium shell runs out of fuel, the TP-AGB starts. Now the star derives its energy from fusion of hydrogen in a thin shell, which restricts the inner helium shell to a thin layer and prevents it fusing stably. However, over periods of 10,000 to 100,000 years, helium from the hydrogen shell burning builds up and the helium shell ignites explosively, a process known as a helium shell flash; the luminosity of the shell flash peaks at thousands of times the total luminosity of the star, but decreases exponentially over just a few years. The shell flash causes the star to expand and cool which shuts off the hydrogen shell burning and causes strong convection in the zone between the two shells; when the helium shell burning nears the base of the hydrogen shell, the increased temperature reignites hydrogen fusion and the cycle begins again. The large but brief increase in luminosity from the helium shell flash produces an increase in the visible brightness of the star of a few tenths of a magnitude for several hundred years, a change unrelated to the brightness variations on periods of tens to hundreds of days that are common in this type of star.
During the thermal pulses, which last only a few hundred years, material from the core region may be mixed into the outer layers, changing the surface composition, a process referred to as dredge-up. Because of this dredge-up, AGB stars may show S-process elements in their spectra and strong dredge-ups can lead to the formation of carbon stars. All dredge-ups following thermal pulses are referred to as third dredge-ups, after the first dredge-up, which occurs on the red-giant branch, the second dredge up, which occurs during the E-AGB. In some cases there may not be a second dredge-up but dredge-ups following thermal pulses will still be called a third dredge-up. Thermal pulses increase in strength after the first few, so third dredge-ups are the deepest and most to circulate core material to the surface. AGB stars are long-period variables, suffer mass loss in the form of a stellar wind. Thermal pulses produce periods of higher mass loss and may result in detached shells of circumstellar material.
A star may lose 50 to 70% of its mass during the AGB phase. The extensive mass loss of AGB stars means that they are surrounded by an extended circumstellar envelope. Given a mean AGB lifetime of one Myr and an outer velocity of 10 km/s, its maximum radius can be estimated to be 3×1014 km; this is a maximum value since the wind material will start to mix with the interstellar medium at large radii, it assumes that there is no velocity difference between the star and the interstellar gas. Dynamically, most of the interesting action is quite close to the star, where the wind is launched and the mass loss rate is determined. However, the outer layers of the CSE show chemically interesting processes, due to size and lower optical depth, are easier to observe; the temperature of the CSE is determined by heating and cooling properties of the gas and dust, but drops with radial distance from the photosphere of the stars which are 2,000–3,000 K. Chemical peculiarities of an AGB CSE outwards include: Photosphere: Local thermodynamic equilibrium chemistry Pulsating stellar envelope: Shock chemistry Dust formation zone Chemically quiet Interstellar ultraviolet radiation and photodissociation of molecules – complex chemistryThe dichotomy between oxygen-rich and carbon-rich stars has an initial role in determining whether the first condensates are oxi
The apparent magnitude of an astronomical object is a number, a measure of its brightness as seen by an observer on Earth. The magnitude scale is logarithmic. A difference of 1 in magnitude corresponds to a change in brightness by a factor of 5√100, or about 2.512. The brighter an object appears, the lower its magnitude value, with the brightest astronomical objects having negative apparent magnitudes: for example Sirius at −1.46. The measurement of apparent magnitudes or brightnesses of celestial objects is known as photometry. Apparent magnitudes are used to quantify the brightness of sources at ultraviolet and infrared wavelengths. An apparent magnitude is measured in a specific passband corresponding to some photometric system such as the UBV system. In standard astronomical notation, an apparent magnitude in the V filter band would be denoted either as mV or simply as V, as in "mV = 15" or "V = 15" to describe a 15th-magnitude object; the scale used to indicate magnitude originates in the Hellenistic practice of dividing stars visible to the naked eye into six magnitudes.
The brightest stars in the night sky were said to be of first magnitude, whereas the faintest were of sixth magnitude, the limit of human visual perception. Each grade of magnitude was considered twice the brightness of the following grade, although that ratio was subjective as no photodetectors existed; this rather crude scale for the brightness of stars was popularized by Ptolemy in his Almagest and is believed to have originated with Hipparchus. In 1856, Norman Robert Pogson formalized the system by defining a first magnitude star as a star, 100 times as bright as a sixth-magnitude star, thereby establishing the logarithmic scale still in use today; this implies that a star of magnitude m is about 2.512 times as bright as a star of magnitude m + 1. This figure, the fifth root of 100, became known as Pogson's Ratio; the zero point of Pogson's scale was defined by assigning Polaris a magnitude of 2. Astronomers discovered that Polaris is variable, so they switched to Vega as the standard reference star, assigning the brightness of Vega as the definition of zero magnitude at any specified wavelength.
Apart from small corrections, the brightness of Vega still serves as the definition of zero magnitude for visible and near infrared wavelengths, where its spectral energy distribution approximates that of a black body for a temperature of 11000 K. However, with the advent of infrared astronomy it was revealed that Vega's radiation includes an Infrared excess due to a circumstellar disk consisting of dust at warm temperatures. At shorter wavelengths, there is negligible emission from dust at these temperatures. However, in order to properly extend the magnitude scale further into the infrared, this peculiarity of Vega should not affect the definition of the magnitude scale. Therefore, the magnitude scale was extrapolated to all wavelengths on the basis of the black-body radiation curve for an ideal stellar surface at 11000 K uncontaminated by circumstellar radiation. On this basis the spectral irradiance for the zero magnitude point, as a function of wavelength, can be computed. Small deviations are specified between systems using measurement apparatuses developed independently so that data obtained by different astronomers can be properly compared, but of greater practical importance is the definition of magnitude not at a single wavelength but applying to the response of standard spectral filters used in photometry over various wavelength bands.
With the modern magnitude systems, brightness over a wide range is specified according to the logarithmic definition detailed below, using this zero reference. In practice such apparent magnitudes do not exceed 30; the brightness of Vega is exceeded by four stars in the night sky at visible wavelengths as well as the bright planets Venus and Jupiter, these must be described by negative magnitudes. For example, the brightest star of the celestial sphere, has an apparent magnitude of −1.4 in the visible. Negative magnitudes for other bright astronomical objects can be found in the table below. Astronomers have developed other photometric zeropoint systems as alternatives to the Vega system; the most used is the AB magnitude system, in which photometric zeropoints are based on a hypothetical reference spectrum having constant flux per unit frequency interval, rather than using a stellar spectrum or blackbody curve as the reference. The AB magnitude zeropoint is defined such that an object's AB and Vega-based magnitudes will be equal in the V filter band.
As the amount of light received by a telescope is reduced by transmission through the Earth's atmosphere, any measurement of apparent magnitude is corrected for what it would have been as seen from above the atmosphere. The dimmer an object appears, the higher the numerical value given to its apparent magnitude, with a difference of 5 magnitudes corresponding to a brightness factor of 100. Therefore, the apparent magnitude m, in the spectral band x, would be given by m x = − 5 log 100 , more expressed in terms of common logarithms as m x
Swan bands are a characteristic of the spectra of carbon stars, comets and of burning hydrocarbon fuels. They are named for the Scottish physicist William Swan, who first studied the spectral analysis of radical diatomic carbon in 1856. Swan bands consist of several sequences of vibrational bands scattered throughout the visible spectrum. Spectroscopy