A brown dwarf is a type of substellar object occupying the mass range between the heaviest gas giant planets and the lightest stars, having a mass between 13 to 75–80 times that of Jupiter, or 2.5×1028 kg to about 1.5×1029 kg. Below this range are the sub-brown dwarfs, above it are the lightest red dwarfs. Brown dwarfs may be convective, with no layers or chemical differentiation by depth. Unlike the stars in the main sequence, brown dwarfs are not massive enough to sustain nuclear fusion of ordinary hydrogen to helium in their cores, they are, thought to fuse deuterium and to fuse lithium if their mass is above a debated threshold of 13 MJ and 65 MJ, respectively. It is debated whether brown dwarfs would be better defined by their formation processes rather than by their supposed nuclear fusion reactions. Stars are categorized by spectral class, with brown dwarfs designated as types M, L, T, Y. Despite their name, brown dwarfs are of different colors. Many brown dwarfs would appear magenta to the human eye, or orange/red.
Brown dwarfs are not luminous at visible wavelengths. There are planets known to orbit brown dwarfs: 2M1207b, MOA-2007-BLG-192Lb, 2MASS J044144b. At a distance of about 6.5 light years, the nearest known brown dwarf is Luhman 16, a binary system of brown dwarfs discovered in 2013. HR 2562 b is listed as the most-massive known exoplanet in NASA's exoplanet archive, despite having a mass more than twice the 13-Jupiter-mass cutoff between planets and brown dwarfs; the objects now called "brown dwarfs" were theorized to exist in the 1960s by Shiv S. Kumar and were called black dwarfs, a classification for dark substellar objects floating in space that were not massive enough to sustain hydrogen fusion. However: the term black dwarf was in use to refer to a cold white dwarf; because of this, alternative names for these objects were proposed, including substar. In 1975, Jill Tarter suggested the term "brown dwarf"; the term "black dwarf" still refers to a white dwarf that has cooled to the point that it no longer emits significant amounts of light.
However, the time required for the lowest-mass white dwarf to cool to this temperature is calculated to be longer than the current age of the universe. Early theories concerning the nature of the lowest-mass stars and the hydrogen-burning limit suggested that a population I object with a mass less than 0.07 solar masses or a population II object less than 0.09 M☉ would never go through normal stellar evolution and would become a degenerate star. The first self-consistent calculation of the hydrogen-burning minimum mass confirmed a value between 0.08 and 0.07 solar masses for population I objects. The discovery of deuterium burning down to 0.012 solar masses and the impact of dust formation in the cool outer atmospheres of brown dwarfs in the late 1980s brought these theories into question. However, such objects were hard to find because they emit no visible light, their strongest emissions are in the infrared spectrum, ground-based IR detectors were too imprecise at that time to identify any brown dwarfs.
Since numerous searches by various methods have sought these objects. These methods included multi-color imaging surveys around field stars, imaging surveys for faint companions of main-sequence dwarfs and white dwarfs, surveys of young star clusters, radial velocity monitoring for close companions. For many years, efforts to discover brown dwarfs were fruitless. In 1988, however, a faint companion to a star known as GD 165 was found in an infrared search of white dwarfs; the spectrum of the companion GD 165B was red and enigmatic, showing none of the features expected of a low-mass red dwarf. It became clear that GD 165B would need to be classified as a much cooler object than the latest M dwarfs known. GD 165B remained unique for a decade until the advent of the Two Micron All-Sky Survey which discovered many objects with similar colors and spectral features. Today, GD 165B is recognized as the prototype of a class of objects now called "L dwarfs". Although the discovery of the coolest dwarf was significant at the time, it was debated whether GD 165B would be classified as a brown dwarf or a very-low-mass star, because observationally it is difficult to distinguish between the two.
Soon after the discovery of GD 165B, other brown-dwarf candidates were reported. Most failed to live up to their candidacy, because the absence of lithium showed them to be stellar objects. True stars burn their lithium within a little over 100 Myr. Hence, the detection of lithium in the atmosphere of an object older than 100 Myr ensures that it is a brown dwarf. In 1995, the study of brown dwarfs changed with the discovery of two indisputable substellar objects – Teide 1 and Gliese 229B – which were identified by the presence of the 670.8 nm lithium line. The latter was found to luminosity well below the stellar range, its near-infrared spectrum exhibited a methane absorption band at 2 micrometres, a feature that had only been observed in the atmospheres of giant planets and that of Saturn's moon Titan. Methane absorption is not expected at any temperature of a main-sequence star; this discovery helped to establish yet another spectral class cooler than L d
The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process, it is by far the most important source of energy for life on Earth. Its diameter is about 1.39 million kilometers, or 109 times that of Earth, its mass is about 330,000 times that of Earth. It accounts for about 99.86% of the total mass of the Solar System. Three quarters of the Sun's mass consists of hydrogen; the Sun is a G-type main-sequence star based on its spectral class. As such, it is informally and not accurately referred to as a yellow dwarf, it formed 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System; the central mass became so hot and dense that it initiated nuclear fusion in its core. It is thought that all stars form by this process.
The Sun is middle-aged. It fuses about 600 million tons of hydrogen into helium every second, converting 4 million tons of matter into energy every second as a result; this energy, which can take between 10,000 and 170,000 years to escape from its core, is the source of the Sun's light and heat. In about 5 billion years, when hydrogen fusion in its core has diminished to the point at which the Sun is no longer in hydrostatic equilibrium, its core will undergo a marked increase in density and temperature while its outer layers expand to become a red giant, it is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury and Venus, render Earth uninhabitable. After this, it will shed its outer layers and become a dense type of cooling star known as a white dwarf, no longer produce energy by fusion, but still glow and give off heat from its previous fusion; the enormous effect of the Sun on Earth has been recognized since prehistoric times, the Sun has been regarded by some cultures as a deity.
The synodic rotation of Earth and its orbit around the Sun are the basis of solar calendars, one of, the predominant calendar in use today. The English proper name Sun may be related to south. Cognates to English sun appear in other Germanic languages, including Old Frisian sunne, Old Saxon sunna, Middle Dutch sonne, modern Dutch zon, Old High German sunna, modern German Sonne, Old Norse sunna, Gothic sunnō. All Germanic terms for the Sun stem from Proto-Germanic *sunnōn; the Latin name for the Sun, Sol, is not used in everyday English. Sol is used by planetary astronomers to refer to the duration of a solar day on another planet, such as Mars; the related word solar is the usual adjectival term used for the Sun, in terms such as solar day, solar eclipse, Solar System. A mean Earth solar day is 24 hours, whereas a mean Martian'sol' is 24 hours, 39 minutes, 35.244 seconds. The English weekday name Sunday stems from Old English and is a result of a Germanic interpretation of Latin dies solis, itself a translation of the Greek ἡμέρα ἡλίου.
The Sun is a G-type main-sequence star. The Sun has an absolute magnitude of +4.83, estimated to be brighter than about 85% of the stars in the Milky Way, most of which are red dwarfs. The Sun is heavy-element-rich, star; the formation of the Sun may have been triggered by shockwaves from more nearby supernovae. This is suggested by a high abundance of heavy elements in the Solar System, such as gold and uranium, relative to the abundances of these elements in so-called Population II, heavy-element-poor, stars; the heavy elements could most plausibly have been produced by endothermic nuclear reactions during a supernova, or by transmutation through neutron absorption within a massive second-generation star. The Sun is by far the brightest object in the Earth's sky, with an apparent magnitude of −26.74. This is about 13 billion times brighter than the next brightest star, which has an apparent magnitude of −1.46. The mean distance of the Sun's center to Earth's center is 1 astronomical unit, though the distance varies as Earth moves from perihelion in January to aphelion in July.
At this average distance, light travels from the Sun's horizon to Earth's horizon in about 8 minutes and 19 seconds, while light from the closest points of the Sun and Earth takes about two seconds less. The energy of this sunlight supports all life on Earth by photosynthesis, drives Earth's climate and weather; the Sun does not have a definite boundary, but its density decreases exponentially with increasing height above the photosphere. For the purpose of measurement, the Sun's radius is considered to be the distance from its center to the edge of the photosphere, the apparent visible surface of the Sun. By this measure, the Sun is a near-perfect sphere with an oblateness estimated at about 9 millionths, which means that its polar diameter differs from its equatorial diameter by only 10 kilometres; the tidal effect of the planets is weak and does not affect the shape of the Sun. The Sun rotates faster at its equator than at its poles; this differential rotation is caused by convective motion
Thermodynamics is the branch of physics that deals with heat and temperature, their relation to energy, work and properties of bodies of matter. The behavior of these quantities is governed by the four laws of thermodynamics, irrespective of the specific composition of the material or system in question; the laws of thermodynamics are explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a wide variety of topics in science and engineering physical chemistry, chemical engineering and mechanical engineering. Thermodynamics developed out of a desire to increase the efficiency of early steam engines through the work of French physicist Nicolas Léonard Sadi Carnot who believed that engine efficiency was the key that could help France win the Napoleonic Wars. Scots-Irish physicist Lord Kelvin was the first to formulate a concise definition of thermodynamics in 1854 which stated, "Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, the relation of heat to electrical agency."
The initial application of thermodynamics to mechanical heat engines was extended early on to the study of chemical compounds and chemical reactions. Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field. Other formulations of thermodynamics emerged in the following decades. Statistical thermodynamics, or statistical mechanics, concerned itself with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909, Constantin Carathéodory presented a purely mathematical approach to the field in his axiomatic formulation of thermodynamics, a description referred to as geometrical thermodynamics. A description of any thermodynamic system employs the four laws of thermodynamics that form an axiomatic basis; the first law specifies that energy can be exchanged between physical systems as work. The second law defines the existence of a quantity called entropy, that describes the direction, thermodynamically, that a system can evolve and quantifies the state of order of a system and that can be used to quantify the useful work that can be extracted from the system.
In thermodynamics, interactions between large ensembles of objects are categorized. Central to this are the concepts of its surroundings. A system is composed of particles, whose average motions define its properties, those properties are in turn related to one another through equations of state. Properties can be combined to express internal energy and thermodynamic potentials, which are useful for determining conditions for equilibrium and spontaneous processes. With these tools, thermodynamics can be used to describe how systems respond to changes in their environment; this can be applied to a wide variety of topics in science and engineering, such as engines, phase transitions, chemical reactions, transport phenomena, black holes. The results of thermodynamics are essential for other fields of physics and for chemistry, chemical engineering, corrosion engineering, aerospace engineering, mechanical engineering, cell biology, biomedical engineering, materials science, economics, to name a few.
This article is focused on classical thermodynamics which studies systems in thermodynamic equilibrium. Non-equilibrium thermodynamics is treated as an extension of the classical treatment, but statistical mechanics has brought many advances to that field; the history of thermodynamics as a scientific discipline begins with Otto von Guericke who, in 1650, built and designed the world's first vacuum pump and demonstrated a vacuum using his Magdeburg hemispheres. Guericke was driven to make a vacuum in order to disprove Aristotle's long-held supposition that'nature abhors a vacuum'. Shortly after Guericke, the English physicist and chemist Robert Boyle had learned of Guericke's designs and, in 1656, in coordination with English scientist Robert Hooke, built an air pump. Using this pump and Hooke noticed a correlation between pressure and volume. In time, Boyle's Law was formulated, which states that pressure and volume are inversely proportional. In 1679, based on these concepts, an associate of Boyle's named Denis Papin built a steam digester, a closed vessel with a fitting lid that confined steam until a high pressure was generated.
Designs implemented a steam release valve that kept the machine from exploding. By watching the valve rhythmically move up and down, Papin conceived of the idea of a piston and a cylinder engine, he did not, follow through with his design. In 1697, based on Papin's designs, engineer Thomas Savery built the first engine, followed by Thomas Newcomen in 1712. Although these early engines were crude and inefficient, they attracted the attention of the leading scientists of the time; the fundamental concepts of heat capacity and latent heat, which were necessary for the development of thermodynamics, were developed by Professor Joseph Black at the University of Glasgow, where James Watt was employed as an instrument maker. Black and Watt performed experiments together, but it was Watt who conceived the idea of the external condenser which resulted in a large increase in steam engine efficiency. Drawing on all the previous work led Sadi Carnot, the "father of thermodynamics", to publish Reflections on the Motive Power of Fire, a discourse on heat, power and engine efficiency.
The book outlined the basic energetic relations between the Carnot engine, the Carnot cycle, motive power. It marked the start of thermodynamics as a modern scien
A conceptual model is a representation of a system, made of the composition of concepts which are used to help people know, understand, or simulate a subject the model represents. It is a set of concepts; some models are physical objects. The term conceptual model may be used to refer to models which are formed after a conceptualization or generalization process. Conceptual models are abstractions of things in the real world whether physical or social. Semantic studies are relevant to various stages of concept formation. Semantics is about concepts, the meaning that thinking beings give to various elements of their experience; the term conceptual model is normal. It could mean "a model of concept" or it could mean "a model, conceptual." A distinction can be made between what models are made of. With the exception of iconic models, such as a scale model of Winchester Cathedral, most models are concepts, but they are intended to be models of real world states of affairs. The value of a model is directly proportional to how well it corresponds to a past, future, actual or potential state of affairs.
A model of a concept is quite different because in order to be a good model it need not have this real world correspondence. In artificial intelligence conceptual models and conceptual graphs are used for building expert systems and knowledge-based systems. Conceptual models range in type from the more concrete, such as the mental image of a familiar physical object, to the formal generality and abstractness of mathematical models which do not appear to the mind as an image. Conceptual models range in terms of the scope of the subject matter that they are taken to represent. A model may, for instance, represent a single thing, whole classes of things, very vast domains of subject matter such as the physical universe; the variety and scope of conceptual models is due to the variety of purposes had by the people using them. Conceptual modeling is the activity of formally describing some aspects of the physical and social world around us for the purposes of understanding and communication." A conceptual model's primary objective is to convey the fundamental principles and basic functionality of the system which it represents.
A conceptual model must be developed in such a way as to provide an understood system interpretation for the model's users. A conceptual model, when implemented properly, should satisfy four fundamental objectives. Enhance an individual's understanding of the representative system Facilitate efficient conveyance of system details between stakeholders Provide a point of reference for system designers to extract system specifications Document the system for future reference and provide a means for collaborationThe conceptual model plays an important role in the overall system development life cycle. Figure 1 below, depicts the role of the conceptual model in a typical system development scheme, it is clear that if the conceptual model is not developed, the execution of fundamental system properties may not be implemented properly, giving way to future problems or system shortfalls. These failures do have been linked to; those weak links in the system design and development process can be traced to improper execution of the fundamental objectives of conceptual modeling.
The importance of conceptual modeling is evident when such systemic failures are mitigated by thorough system development and adherence to proven development objectives/techniques. As systems have become complex, the role of conceptual modelling has expanded. With that expanded presence, the effectiveness of conceptual modeling at capturing the fundamentals of a system is being realized. Building on that realization, numerous conceptual modeling techniques have been created; these techniques can be applied across multiple disciplines to increase the user's understanding of the system to be modeled. A few techniques are described in the following text, many more exist or are being developed; some used conceptual modeling techniques and methods include: workflow modeling, workforce modeling, rapid application development, object-role modeling, the Unified Modeling Language. Data flow modeling is a basic conceptual modeling technique that graphically represents elements of a system. DFM is a simple technique, like many conceptual modeling techniques, it is possible to construct higher and lower level representative diagrams.
The data flow diagram does not convey complex system details such as parallel development considerations or timing information, but rather works to bring the major system functions into context. Data flow modeling is a central technique used in systems development that utilizes the structured systems analysis and design method. Entity-relationship modeling is a conceptual modeling technique used for software system representation. Entity-relationship diagrams, which are a product of executing the ERM technique, are used to represent database models and information systems; the main components of the diagram are the relationships. The entities can represent objects, or events; the relationships are responsible for relating the entities to one another. To form a system process, the relationships are combined with the entities and any attr
Astrophysics is the branch of astronomy that employs the principles of physics and chemistry "to ascertain the nature of the astronomical objects, rather than their positions or motions in space". Among the objects studied are the Sun, other stars, extrasolar planets, the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, the properties examined include luminosity, density and chemical composition; because astrophysics is a broad subject, astrophysicists apply concepts and methods from many disciplines of physics, including mechanics, statistical mechanics, quantum mechanics, relativity and particle physics, atomic and molecular physics. In practice, modern astronomical research involves a substantial amount of work in the realms of theoretical and observational physics; some areas of study for astrophysicists include their attempts to determine the properties of dark matter, dark energy, black holes.
Topics studied by theoretical astrophysicists include Solar System formation and evolution. Astronomy is an ancient science, long separated from the study of terrestrial physics. In the Aristotelian worldview, bodies in the sky appeared to be unchanging spheres whose only motion was uniform motion in a circle, while the earthly world was the realm which underwent growth and decay and in which natural motion was in a straight line and ended when the moving object reached its goal, it was held that the celestial region was made of a fundamentally different kind of matter from that found in the terrestrial sphere. During the 17th century, natural philosophers such as Galileo and Newton began to maintain that the celestial and terrestrial regions were made of similar kinds of material and were subject to the same natural laws, their challenge was. For much of the nineteenth century, astronomical research was focused on the routine work of measuring the positions and computing the motions of astronomical objects.
A new astronomy, soon to be called astrophysics, began to emerge when William Hyde Wollaston and Joseph von Fraunhofer independently discovered that, when decomposing the light from the Sun, a multitude of dark lines were observed in the spectrum. By 1860 the physicist, Gustav Kirchhoff, the chemist, Robert Bunsen, had demonstrated that the dark lines in the solar spectrum corresponded to bright lines in the spectra of known gases, specific lines corresponding to unique chemical elements. Kirchhoff deduced that the dark lines in the solar spectrum are caused by absorption by chemical elements in the Solar atmosphere. In this way it was proved that the chemical elements found in the Sun and stars were found on Earth. Among those who extended the study of solar and stellar spectra was Norman Lockyer, who in 1868 detected bright, as well as dark, lines in solar spectra. Working with the chemist, Edward Frankland, to investigate the spectra of elements at various temperatures and pressures, he could not associate a yellow line in the solar spectrum with any known elements.
He thus claimed the line represented a new element, called helium, after the Greek Helios, the Sun personified. In 1885, Edward C. Pickering undertook an ambitious program of stellar spectral classification at Harvard College Observatory, in which a team of woman computers, notably Williamina Fleming, Antonia Maury, Annie Jump Cannon, classified the spectra recorded on photographic plates. By 1890, a catalog of over 10,000 stars had been prepared that grouped them into thirteen spectral types. Following Pickering's vision, by 1924 Cannon expanded the catalog to nine volumes and over a quarter of a million stars, developing the Harvard Classification Scheme, accepted for worldwide use in 1922. In 1895, George Ellery Hale and James E. Keeler, along with a group of ten associate editors from Europe and the United States, established The Astrophysical Journal: An International Review of Spectroscopy and Astronomical Physics, it was intended that the journal would fill the gap between journals in astronomy and physics, providing a venue for publication of articles on astronomical applications of the spectroscope.
Around 1920, following the discovery of the Hertsprung-Russell diagram still used as the basis for classifying stars and their evolution, Arthur Eddington anticipated the discovery and mechanism of nuclear fusion processes in stars, in his paper The Internal Constitution of the Stars. At that time, the source of stellar energy was a complete mystery; this was a remarkable development since at that time fusion and thermonuclear energy, that stars are composed of hydrogen, had not yet been discovered. In 1
The density, or more the volumetric mass density, of a substance is its mass per unit volume. The symbol most used for density is ρ, although the Latin letter D can be used. Mathematically, density is defined as mass divided by volume: ρ = m V where ρ is the density, m is the mass, V is the volume. In some cases, density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more called specific weight. For a pure substance the density has the same numerical value as its mass concentration. Different materials have different densities, density may be relevant to buoyancy and packaging. Osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity "relative density" or "specific gravity", i.e. the ratio of the density of the material to that of a standard material water.
Thus a relative density less than one means. The density of a material varies with pressure; this variation is small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object and thus increases its density. Increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a fluid results in convection of the heat from the bottom to the top, due to the decrease in the density of the heated fluid; this causes it to rise relative to more dense unheated material. The reciprocal of the density of a substance is called its specific volume, a term sometimes used in thermodynamics. Density is an intensive property in that increasing the amount of a substance does not increase its density. In a well-known but apocryphal tale, Archimedes was given the task of determining whether King Hiero's goldsmith was embezzling gold during the manufacture of a golden wreath dedicated to the gods and replacing it with another, cheaper alloy.
Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated and compared with the mass. Baffled, Archimedes is said to have taken an immersion bath and observed from the rise of the water upon entering that he could calculate the volume of the gold wreath through the displacement of the water. Upon this discovery, he leapt from his bath and ran naked through the streets shouting, "Eureka! Eureka!". As a result, the term "eureka" entered common parlance and is used today to indicate a moment of enlightenment; the story first appeared in written form in Vitruvius' books of architecture, two centuries after it took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time. From the equation for density, mass density has units of mass divided by volume; as there are many units of mass and volume covering many different magnitudes there are a large number of units for mass density in use.
The SI unit of kilogram per cubic metre and the cgs unit of gram per cubic centimetre are the most used units for density. One g/cm3 is equal to one thousand kg/m3. One cubic centimetre is equal to one millilitre. In industry, other larger or smaller units of mass and or volume are more practical and US customary units may be used. See below for a list of some of the most common units of density. A number of techniques as well as standards exist for the measurement of density of materials; such techniques include the use of a hydrometer, Hydrostatic balance, immersed body method, air comparison pycnometer, oscillating densitometer, as well as pour and tap. However, each individual method or technique measures different types of density, therefore it is necessary to have an understanding of the type of density being measured as well as the type of material in question; the density at all points of a homogeneous object equals its total mass divided by its total volume. The mass is measured with a scale or balance.
To determine the density of a liquid or a gas, a hydrometer, a dasymeter or a Coriolis flow meter may be used, respectively. Hydrostatic weighing uses the displacement of water due to a submerged object to determine the density of the object. If the body is not homogeneous its density varies between different regions of the object. In that case the density around any given location is determined by calculating the density of a small volume around that location. In the limit of an infinitesimal volume the density of an inhomogeneous object at a point becomes: ρ = d m / d V, where d V is an elementary volume at position r; the mass of the body t
Sir Franz Arthur Friedrich Schuster FRS FRSE was a German-born British physicist known for his work in spectroscopy, optics, X-radiography and the application of harmonic analysis to physics. Schuster's integral is named after him, he contributed to making the University of Manchester a centre for the study of physics. Arthur Schuster was born in Frankfurt am Main, Germany the son of Francis Joseph Schuster, a cotton merchants and banker, his wife Marie Pfeiffer. Schuster's parents were married in 1849, converted from Judaism to Christianity, brought up their children in that faith. In 1869, his father moved to Manchester. Arthur, to school in Frankfurt and was studying in Geneva, joined his parents in 1870 and he and the other children became British citizens in 1875. Edgar Schuster was his nephew. From his childhood, Schuster had been interested in science and after working for a year for the family firm of Schuster Brothers in Manchester, he persuaded his father to let him study at Owens College.
He studied mathematics under Thomas Barker and physics under Balfour Stewart, began research with Henry Roscoe on the spectra of hydrogen and nitrogen. He spent a year with Gustav Kirchhoff at the University of Heidelberg, having gained his PhD, returned to Owens as an unpaid demonstrator in physics. Schuster used his family's wealth to buy material and equipment and to endow readerships in mathematical physics at Manchester and meteorology at the University of Cambridge, he contributed to the Royal Society and the International Union for Co-operation in Solar Research. After a further period of study in Germany with Wilhelm Eduard Weber and Hermann von Helmholtz, he returned to England, where his knowledge of spectrum analysis led to him being appointed to lead an expedition to Siam, to photograph the coronal spectrum during the total solar eclipse of 6 April 1875; this was an important appointment for such a junior scientist. On the way, he wrote a letter dated 21 February 1875, to Nature describing his observation of the "green flash" phenomenon.
On his return to Manchester in 1875, he began research on electricity and went on to spend five years at the Cavendish Laboratory of the University of Cambridge. His status there was quite unofficial, he worked with Rayleigh. In 1881, he was appointed to the Beyer Chair of Applied Mathematics at Owens, by now one of the colleges of the new Victoria University, he succeeded his teacher Balfour Stewart as professor of physics in 1888. This appointment gave him the opportunity to establish a large, active teaching and research department. In 1900 a new laboratory, for which he had fought and which he had designed, was opened, it was the fourth largest in the world. The laboratory became a serious rival to the Cavendish. Much of this fame was associated with Ernest Rutherford who succeeded Schuster as Langworthy Professor in 1907. Schuster resigned from the chair for health reasons and to promote the cause of international science, he ensured. Schuster is credited with coining the concept of antimatter in two letters to Nature in 1898.
He hypothesized antiatoms, whole antimatter solar systems, which would yield energy if the atoms combined with atoms of normal matter. His hypothesis was given a mathematical foundation by the work of Paul Dirac in 1928, which predicted antiparticles and led to their discovery. Schuster is most remembered for his periodogram analysis, a technique, long the main practical tool for identifying statistically important frequencies present in a time series of observations, he first used this form of harmonic analysis in 1897 to disprove C. G. Knott's claim of periodicity in earthquake occurrences, he went on to apply the technique to analysing sunspot activity. This was an old interest. In 1875 Stewart's friend and Roscoe's cousin, the economist Jevons, reported, "Mr. A Schuster of Owens College has ingeniously pointed out that the periods of good vintage in Western Europe have occurred at intervals somewhat approximating to eleven years, the average length of the principal sun-spot cycle." Schuster is credited by Chandrasekhar to have given a fresh start to the radiative transfer problem.
Schuster formulated in 1905 a problem in radiative transfer in an attempt to explain the appearance of absorption and emission lines in stellar spectra. This was the first use of the two-stream approximation that underpins the treatment of radiative transfer in all weather and climate models. In 1912 he bought Yeldall House near Berkshire. Following the outbreak of World War I in 1914, the Schuster family was subjected to anti-German prejudice in the press and, in Arthur's case, in some quarters of the Royal Society, his brother Sir Felix Schuster had to issue a statement pointing out the family's loyalty to Britain and that they all had sons serving in the British army. On the day Arthur gave his presidential address to the 1915 British Association meeting, he learned that his son had been wounded. Schuster was regarded by his contemporaries as a mathematical physicist of exceptional ability but as a capable administrator and teacher, an advocate for the role of science in education and industry.
He died in Twyford on 14 October 1934. He is buried in Brookwood Cemetery in outer London. In 1887 he married Caroline Loveday. Schuster was elected a Fellow of the Royal Society in 1879, knighted in the 1920 New Year Honours. Other honours include doctorates from the universities of Calcutta, Geneva, St Andrews, and