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Encyclopedia > Binary star
Hubble image of the Sirius binary system, in which Sirius B can be clearly distinguished (lower left).
Hubble image of the Sirius binary system, in which Sirius B can be clearly distinguished (lower left).

A binary star is a stellar system consisting of two stars orbiting around their center of mass. For each star, the other is its companion star. Recent research suggests that a large percentage of stars are part of systems with at least two stars. Binary star systems are very important in astrophysics, because observing their mutual orbits allows their mass to be determined. The masses of many single stars can then be determined by extrapolations made from the observation of binaries. Binary Star were an underground rap group formed in 1998 that comprised of OneBeLo and Senim Silla. ... Image File history File linksMetadata Sirius_A_and_B_Hubble_photo. ... Image File history File linksMetadata Sirius_A_and_B_Hubble_photo. ... The Hubble Space Telescope (HST; also known colloquially as the Hubble or just Hubble) is a space telescope that was carried into Earth orbit by the Space Shuttle in April 1990. ... This article is about the brightest star in the night sky of Earth. ... A star system or stellar system is a small number of stars that orbit each other,[1] bound by gravitational attraction. ... This article is about the astronomical object. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... In physics, the center of mass of a system of particles is a specific point at which, for many purposes, the systems mass behaves as if it were concentrated. ... Spiral Galaxy ESO 269-57 Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties (luminosity, density, temperature, and chemical composition) of celestial objects such as stars, galaxies, and the interstellar medium, as well as their interactions. ... For other uses, see Mass (disambiguation). ...


Binary stars are not the same as optical double stars, which appear to be close together as seen from Earth, but may not be bound noticeably by gravity. Binary stars can either be distinguished optically (visual binaries) or by indirect techniques, such as spectroscopy. If binaries happen to orbit in a plane containing our line of sight, they will eclipse each other; these are called eclipsing binaries. When two stars are so nearly in the same direction as seen from Earth that they appear to be a single star to the naked eye but may be separated by the use of telescopes, they are referred to as a double star. ... This article is about Earth as a planet. ... Gravity redirects here. ... Animation of the dispersion of light as it travels through a triangular prism. ... This article is about astronomical eclipses. ...


Systems consisting of more than two components, known as multiple stars, are also not uncommon and are generally classified under the same name. The components of binary star systems can exchange mass, bringing their evolution to stages that single stars cannot attain. Examples of binaries are Algol (an eclipsing binary), Sirius, and Cygnus X-1 (of which one member is probably a black hole). Artists impression of the orbits of HD 188753, a triple star system A multiple star consists of three or more stars which appear from the Earth to be close to one another. ... Projected timeline of the Suns life In astronomy, stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. ... It has been suggested that ALGOL object code be merged into this article or section. ... This article is about the brightest star in the night sky of Earth. ... Location of the X-ray source Cygnus X-1, which is widely accepted to be a 10 solar mass black hole orbiting a blue giant star. ... For other uses, see Black hole (disambiguation). ...

Contents

Terminology

The term binary star was coined by Sir William Herschel in 1802 to designate, in his definition, "a real double star - the union of two stars that are formed together in one system by the laws of attraction". Any two closely-spaced stars might appear to be a double star, the most famous case being Mizar and Alcor in the Big Dipper (Ursa Major). It is however possible that a double star is merely a star pair that only looks like a binary system: the two stars can in reality be widely separated in space, but just happen to lie in roughly the same direction as seen from Earth. Such false binaries are termed optical binaries, or optical pairs. With the invention of the telescope, many such pairs were found. Herschel, in 1780, measured the separation and orientations of over 700 pairs that appeared to be binary systems, and found that about 50 pairs changed orientation over two decades of observation.[1][2] A neologism is a word, term, or phrase which has been recently created (or coined), often to apply to new concepts, to synthesize pre-existing concepts, or to make older terminology sound more contemporary. ... For other persons named William Herschel, see William Herschel (disambiguation). ... When two stars are so nearly in the same direction as seen from Earth that they appear to be a single star to the naked eye but may be separated by the use of telescopes, they are referred to as a double star. ... Mizar (ζ UMa) is a star in the constellation Ursa Major, lying just at the corner of the Big Dippers handle. ... Big Dipper map A group of the brightest stars of the constellation Ursa Major, the Great Bear, form a well-known asterism that has been recognized as a distinct grouping in many cultures from time immemorial. ... This article is about the constellation. ... This article does not cite any references or sources. ...


A true binary is a pair of stars bound together by gravity. When they can be resolved (distinguished) with a powerful enough telescope (if necessary with the aid of interferometric methods) they are known as visual binaries.[3][4] In other cases, the only indication is the Doppler shift of the emitted light. Systems in which this is the case, known as spectroscopic binaries, consist of relatively close pairs of stars where the spectral lines in the light from each one shifts first toward the blue, then toward the red, as each moves first toward us, and then away from us, during its motion about their common center of mass, with the period of their common orbit. If the orbital plane is very nearly along our line of sight, the two stars partially or fully occult each other regularly, and the system is called an eclipsing binary, of which Algol is the best-known example.[5] Gravity redirects here. ... Resolving power is the ability of a microscope or telescope to measure the angular separation of images that are close together. ... It has been suggested that Optical interferometry be merged into this article or section. ... A source of waves moving to the left. ... For other uses, see Light (disambiguation). ... A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ... In physics, the center of mass of a system of particles is a specific point at which, for many purposes, the systems mass behaves as if it were concentrated. ... In this July, 1997 still frame captured from video, the bright star Aldebaran has just reappeared on the dark limb of the waning crescent moon in this predawn occultation. ... It has been suggested that ALGOL object code be merged into this article or section. ...


Binary stars that are both visual and spectroscopic binaries are rare, and are a precious source of valuable information when found. Visual binary stars often have large true separations, with periods measured in decades to centuries; consequently, they usually have orbital speeds too small to be measured spectroscopically. Conversely, spectroscopic binary stars move fast in their orbits because they are close together; usually too close to be detected as visual binaries. Binaries that are both visual and spectroscopic thus must be relatively close to Earth.


Astronomers have discovered some stars that seem to orbit around an empty space. Astrometric binaries are relatively nearby stars which can be seen to wobble around a middle point, with no visible companion. With some spectroscopic binaries, there is only one set of lines shifting back and forth. The same mathematics used for ordinary binaries can be applied to infer the mass of the missing companion. The companion could be very dim, so that it is currently undetectable or masked by the glare of its primary, or it could be an object that emits little or no electromagnetic radiation, for example a neutron star.[6] In some instances, there is strong evidence that the missing companion is in fact a black hole: a body with such strong gravity that no light is able to escape. Such binaries are known as high-mass X-ray binaries. Probably the best known example at present is Cygnus X-1, where the mass of the unseen companion is believed to be about nine times that of our sun; far exceeding the Tolman-Oppenheimer-Volkoff limit (the maximum theoretical mass of a neutron star, the only other likely candidate for the companion). In this way, Cygnus X-1 became the first object that was widely accepted as being a black hole.[7][8] For other uses, see Mass (disambiguation). ... This box:      Electromagnetic (EM) radiation is a self-propagating wave in space with electric and magnetic components. ... For the story by Larry Niven, see Neutron Star (story). ... For other uses, see Black hole (disambiguation). ... A high-mass X-ray binary (HMXB) is a binary star where one of the components is a neutron star or a black hole. ... Location of the X-ray source Cygnus X-1, which is widely accepted to be a 10 solar mass black hole orbiting a blue giant star. ... This article is in need of attention from an expert on the subject. ...


Classifications

By methods of observation

Binary stars are classified into four types according to their observable properties.[9] Any binary star can belong to several of these classes; for example, several spectroscopic binaries are also eclipsing binaries.


Visual binaries

A visual binary star is a binary star for which the angular separation between the two components is great enough to permit them to be observed as a double star in a telescope. The resolving power of the telescope is an important factor in the detection of visual binaries, and as telescopes become larger and more powerful an increasing number of visual binaries will be detected. The brightness of the two stars is also an important factor, as brighter stars are harder to separate due to their glare than dimmer ones are. This article is about the astronomical object. ... When two stars are so nearly in the same direction as seen from Earth that they appear to be a single star to the naked eye but may be separated by the use of telescopes, they are referred to as a double star. ... This article does not cite any references or sources. ... Angular resolution describes the resolving power of any optical device such as a telescope, a microscope, a camera, or an eye. ...


The brighter star of a visual binary is the primary star, and the dimmer is considered the secondary. In some publications (especially older ones), a faint secondary is called the comes; if the stars are the same brightness, the discoverer "chooses" the primary.[10] The position angle of the secondary with respect to the primary is measured, together with the angular distance between the two stars. The time of observation is also recorded. After a sufficient number of observations are recorded over a period of time, they are plotted in polar coordinates with the primary star at the origin, and the most probable ellipse is drawn through these points such that the Keplerian law of areas is satisfied. This ellipse is known as the apparent ellipse, and is the projection of the actual elliptical orbit of the secondary with respect to the primary on the plane of the sky. From this projected ellipse the complete elements of the orbit may be computed, with the semi-major axis being expressed in angular units unless the stellar parallax, and hence the distance, of the system is known.[3] Position angle, usually abbreviated PA, is a measurement derived from observing visual binary stars. ... Coordinates are numbers which describe the location of points in a plane or in space. ... For other uses, see Ellipse (disambiguation). ... Illustration of Keplers three laws with two planetary orbits. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae. ... For other uses, see Parallax (disambiguation). ...


Spectroscopic binaries

A spectroscopic binary star is a binary star in which the separation between the stars is usually very small, and the orbital velocity very high. Unless the plane of the orbit happens to be perpendicular to the line of sight, the orbital velocities will have components in the line of sight and the observed radial velocity of the system will vary periodically. Since radial velocity can be measured with a spectrometer by observing the Doppler shift of the stars' spectral lines, the binaries detected in this manner are known as spectroscopic binaries. Most of these cannot be resolved as a visual binary, even with telescopes of the highest existing resolving power. Two bodies with a slight difference in mass orbiting around a common barycenter. ... Radial velocity is the velocity of an object in the direction of the line of sight. ... Spectrometer A spectrometer is an optical instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. ... A source of waves moving to the left. ... A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ... This article does not cite any references or sources. ... Resolving power is the ability of a microscope or telescope to measure the angular separation of images that are close together. ...


In some spectroscopic binaries, spectral lines from both stars are visible and the lines are alternately double and single. Such a system is known as a double-lined spectroscopic binary (often denoted "SB2"). In other systems, the spectrum of only one of the stars is seen and the lines in the spectrum shift periodically towards the blue, then towards red and back again. Such stars are known as single-lined spectroscopic binaries ("SB1").


The orbit of a spectroscopic binary is determined by making a long series of observations of the radial velocity of one or both components of the system. The observations are plotted against time, and from the resulting curve a period is determined. If the orbit is circular then the curve will be a sine curve. If the orbit is elliptical, the shape of the curve will depend on the eccentricity of the ellipse and the orientation of the major axis with reference to the line of sight. Two bodies with a slight difference in mass orbiting around a common barycenter. ... This article is about the shape and mathematical concept of circle. ... Sine redirects here. ... For other uses, see Ellipse (disambiguation). ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ...


It is impossible to determine individually the semi-major axis a and the inclination of the orbit plane i. However, the product of the semi-major axis and the sine of the inclination (i.e. a sin i) may be determined directly in linear units (e.g. kilometres). If either a or i can be determined by other means, as in the case of eclipsing binaries, a complete solution for the orbit can be found.[11] The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae. ...


Eclipsing binaries

An eclipsing binary, with an indication of the variation in intensity.
An eclipsing binary, with an indication of the variation in intensity.[12][13]

An eclipsing binary star is a binary star in which the orbit plane of the two stars lies so nearly in the line of sight of the observer that the components undergo mutual eclipses. In the case where the binary is also a spectroscopic binary and the parallax of the system is known, the binary is quite valuable for stellar analysis.[14] Image File history File links Eclipsing_binary_star_animation_2. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... This article is about the astronomical object. ... This article is about astronomical eclipses. ... For other uses, see Parallax (disambiguation). ...


In the last decade, measurement of eclipsing binaries' fundamental parameters has become possible with 8 meter class telescopes. This makes it feasible to use them as standard candles. Recently, they have been used to give direct distance estimates to the LMC, SMC, Andromeda Galaxy and Triangulum Galaxy. Eclipsing binaries offer a direct method to gauge the distance to galaxies to a new improved 5% level of accuracy.[15] A standard candle is an astronomical object that has a known luminosity. ... The Large Magellanic Cloud (LMC) is a nearby satellite galaxy of our own galaxy, the Milky Way. ... The Small Magellanic Cloud (SMC) is a dwarf galaxy[1] in orbit around the Milky Way Galaxy. ... The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; often referred to as the Great Andromeda Nebula in older texts) is a spiral galaxy approximately 2. ... The Triangulum Galaxy (also known as Messier 33 or NGC 598) is a spiral galaxy about 3. ...


Eclipsing binaries are variable stars, not because the light of the individual components vary but because of the eclipses. The light curve of an eclipsing binary is characterized by periods of practically constant light, with periodic drops in intensity. If one of the stars is larger than the other, one will be obscured by a total eclipse while the other will be obscured by an annular eclipse. This article or section contains a plot summary that is overly long or excessively detailed. ... In astronomy, a light curve is a graph of light intensity as a function of time. ... Annular, annulate, &c. ...


The period of the orbit of an eclipsing binary may be determined from a study of the light curve, and the relative sizes of the individual stars can be determined in terms of the radius of the orbit by observing how quickly the brightness changes as the disc of the near star slides over the disc of the distant star. If it is also a spectroscopic binary the orbital elements can also be determined, and the mass of the stars can be determined relatively easily, which means that the relative densities of the stars can be determined in this case.[16] Two bodies with a slight difference in mass orbiting around a common barycenter. ... The elements of an orbit are the parameters needed to specify that orbit uniquely, given a model of two ideal masses obeying the Newtonian laws of motion and the inverse-square law of gravitational attraction. ...


Astrometric binaries

An astrometric binary star is a binary star for which only one of the component stars can be visually observed. The visible star's position is carefully measured and detected to have a wobble, due to the gravitational influence from its counterpart. The position of the star is repeatedly measured relative to more distant stars, and then checked for periodic shifts in position. Typically this type of measurement can only be performed on nearby stars, such as those within 10 parsecs. Nearby stars often have a relatively high proper motion, so astrometric binaries will appear to follow a sinusoidal path across the sky. A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond. ... The proper motion of a star is the motion of the position of the star in the sky (the change in direction in which we see it, as opposed to the radial velocity) after eliminating the improper motions of the stars, which affect their measured coordinates but are not real... In trigonometry, an ideal sine wave is a waveform whose graph is identical to the generalized sine function y = Asin[ω(x − α)] + C, where A is the amplitude, ω is the angular frequency (2π/P where P is the wavelength), α is the phase shift, and C is the...


If the companion is sufficiently massive to cause an observable shift in position of the star, then its presence can be deduced. From precise astrometric measurements of the movement of the visible star over a sufficiently long period of time, information about the mass of the companion and its orbital period can be determined.[17] Even though the companion is not visible, the characteristics of the system can be determined from the observations using Kepler's laws.[18] Illustration of the use of optical wavelength interferometry to determine precise positions of stars. ... Kepler redirects here. ... Illustration of Keplers three laws with two planetary orbits. ...


This method of detecting binaries is also used to locate extrasolar planets orbiting a star. However, the requirements to perform this measurement are very exacting, due to the great difference in the mass ratio, and the typically long period of the planet's orbit. Detection of position shifts of a star is a very exacting science, and it is difficult to achieve the necessary precision. Space telescopes can avoid the bluring effect of the Earth's atmosphere, resulting in more precise resolution. Any planet is an extremely faint light source compared to its parent star. ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... Air redirects here. ...


By configuration of the system

Artist's conception of a cataclysmic variable system.
Artist's conception of a cataclysmic variable system.

Another classification is based on the distance of the stars, relative to their sizes:[19] Artists conception of a cataclysmic variable system Cataclysmic variables (also U Geminorum Stars) are a class of binary stars containing a white dwarf and a companion star. ...


Detached binaries are a kind of binary stars where each component is within its Roche lobe, i.e. the area where the gravitational pull of the star itself is larger than that of the other component. The stars have no major effect on each other, and essentially evolve separately. Most binaries belong to this class. A three-dimensional representation of the Roche potential in a binary star with a mass ratio of 2, in the co-rotating frame. ... Gravity redirects here. ...


Semidetached binary stars are binary stars where one of the components fills the binary star's Roche lobe and the other does not. Gas from the surface of the Roche lobe filling component (donor) is transferred to the other, accreting star. The mass transfer dominates the evolution of the system. In many cases, the inflowing gas forms an accretion disc around the accretor. Examples of this type are X-ray binaries and Cataclysmic variable stars. Mass transfer is the phrase commonly used in engineering for physical processes that involve molecular and convective transport of atoms and molecules within physical systems. ... Artists conception of a binary star system with one black hole and one main sequence star Unsolved problems in physics: Accretion disc jets: Why do the discs surrounding certain objects, such as the nuclei of active galaxies, emit radiation jets along their polar axes? These jets are invoked by... X-ray binaries are a class of binary stars that are very luminous in X-rays. ... Artists conception of a cataclysmic variable system Cataclysmic variables (also U Geminorum Stars) are a class of binary stars containing a white dwarf and a companion star. ...


A contact binary is a type of binary star in which both components of the binary fill their Roche lobes. The uppermost part of the stellar atmospheres forms a common envelope that surrounds both stars. As the friction of the envelope brakes the orbital motion, the stars may eventually merge.[20] Photo taken during the French 1999 eclipse The stellar atmosphere is the outer region of the volume of a star, lying above the stellar core, radiation zone and convection zone. ... In physics, orbital motion is the either a motion of a planet in a planetary orbit, or a motion of an electron around the nucleus of an atom, or any other motion of parts of a bound system. ...


Binary star evolution

Formation

While it is not impossible that some binaries might be created through gravitational capture between two single stars, given the very low likelihood of such an event (three objects are actually required, as conservation of energy rules out a single gravitating body capturing another) and the high number of binaries, this cannot be the primary formation process. Also, the observation of binaries consisting of pre main sequence stars, supports the theory that binaries are already formed during star formation. Fragmentation of the molecular cloud during the formation of protostars is an acceptable explanation for the formation of a binary or multiple star system.[21][22] Gravity redirects here. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. ... A Protostar is an object that forms by contraction out of the gas of a giant molecular cloud in the interstellar medium. ...


The outcome of the three body problem, where the three stars are of comparable mass, is that eventually one of the three stars will be ejected from the system and, assuming no significant further perturbations, the remaining two will form a stable binary system. The n-body problem is the problem of finding, given the initial positions, masses, and velocities of n bodies, their subsequent motions as determined by classical mechanics, i. ...


Mass transfer and accretion

As a main sequence star increases in size during its evolution, it may at some point exceed its Roche lobe, meaning that some of its matter ventures into a region where the gravitational pull of its companion star is larger than its own.[23] The result is that matter will transfer from one star to another through a process known as Roche Lobe overflow (RLOF), either being absorbed by direct impact or through an accretion disc. The mathematical point through which this transfer happens is called the first Lagrangian point[24]. It is not uncommon that the accretion disc is the brightest (and thus sometimes the only visible) element of a binary star. Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... Projected timeline of the Suns life In astronomy, stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. ... A three-dimensional representation of the Roche potential in a binary star with a mass ratio of 2, in the co-rotating frame. ... Gravity redirects here. ... Artists conception of a binary star system with one black hole and one main sequence star Unsolved problems in physics: Accretion disc jets: Why do the discs surrounding certain objects, such as the nuclei of active galaxies, emit radiation jets along their polar axes? These jets are invoked by... For other meanings of mathematics or uses of math and maths, see Mathematics (disambiguation) and Math (disambiguation). ... A contour plot of the effective potential (the Hills Surfaces) of a two-body system (the Sun and Earth here), showing the five Lagrange points. ...

An animation of an eclipsing binary system undergoing mass transfer.
An animation of an eclipsing binary system undergoing mass transfer.

If a star grows outside of its Roche lobe too fast for all abundant matter to be transferred to the other component, it is also possible that matter will leave the system through other Lagrange points or as stellar wind, thus being effectively lost to both components.[25] Since the evolution of a star is determined by its mass, the process influences the evolution of both companions, and creates stages that can not be attained by single stars.[26][27] Image File history File links Eclipsing_binary_star_animation_3. ... This article is about matter in physics and chemistry. ... A solar wind is a stream of particles (mostly high-energy protons ~ 500 keV) which are ejected from the upper atmosphere of a star (in the case of a star other than the Earths Sun, it may be called a stellar wind instead). ... This article is about the astronomical object. ...


Studies of the eclipsing ternary Algol led to the Algol paradox in the theory of stellar evolution: although components of a binary star form at the same time, and massive stars evolve much faster than the less massive ones, it was observed that the more massive component Algol A is still in the main sequence, while the less massive Algol B is a subgiant star at a later evolutionary stage. The paradox can be solved by mass transfer: when the more massive star became a subgiant, it filled its Roche lobe, and most of the mass was transferred to the other star, which is still in the main sequence. In some binaries similar to Algol, a gas flow can actually be seen.[28] It has been suggested that ALGOL object code be merged into this article or section. ... Projected timeline of the Suns life In astronomy, stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... Subgiant star is a class of stars that are brighter than normal main sequence (dwarf) stars, but not as bright as true giant stars. ... Mass transfer is the phrase commonly used in engineering for physical processes that involve molecular and convective transport of atoms and molecules within physical systems. ... A three-dimensional representation of the Roche potential in a binary star with a mass ratio of 2, in the co-rotating frame. ...


Runaways and novae

A Chandra X-ray Observatory image of the remnants of the SN 1572 supernova.
A Chandra X-ray Observatory image of the remnants of the SN 1572 supernova.

It is also possible for widely separated binaries to lose gravitational contact with each other during their lifetime, as a result of external perturbations. The components will then move on to evolve as single stars. A close encounter between two binary systems can also result in the gravitational disruption of both systems, with some of the stars being ejected at high velocities, leading to runaway stars.[29][30] Image File history File links Download high resolution version (2400x2400, 609 KB) Summary Tychos Supernova Remnant. ... Image File history File links Download high resolution version (2400x2400, 609 KB) Summary Tychos Supernova Remnant. ... The Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. ... X-ray image of the expanding cloud of debris and high energy electrons from Tychos supernova. ... It has been suggested that this article or section be merged into Hypervelocity_star. ...


If a white dwarf has a close companion star that overflows its Roche lobe, the white dwarf will steadily accrete gases from the star's outer atmosphere. These are compacted on the white dwarf's surface by its intense gravity, compressed and heated to very high temperatures as additional material is drawn in. The white dwarf consists of degenerate matter, and so is largely unresponsive to heat, while the accreted hydrogen is not. Hydrogen fusion can occur in a stable manner on the surface through the CNO cycle, causing the enormous amount of energy liberated by this process to blow the remaining gases away from the white dwarf's surface. The result is an extremely bright outburst of light, known as a nova.[31] This article or section does not adequately cite its references or sources. ... A three-dimensional representation of the Roche potential in a binary star with a mass ratio of 2, in the co-rotating frame. ... Degenerate matter is matter which has sufficiently high density that the dominant contribution to its pressure arises from the Pauli exclusion principle. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing sustainable fusion power. ... This article does not cite its references or sources. ... Artists conception of a white dwarf star accreting hydrogen from a larger companion A nova (pl. ...


In extreme cases this event can cause the white dwarf to exceed the Chandrasekhar limit and trigger a supernova that destroys the entire star, and is another possible cause for runaways.[32][33] A famous example of such an event is the supernova SN 1572, which was observed by Tycho Brahe. The Hubble Space Telescope recently took a picture of the remnants of this event. The Chandrasekhar limit (named after the Indian astrophysicist Subrahmanyan Chandrasekhar) is the maximum nonrotating mass which can be supported against gravitational collapse by electron degeneracy pressure. ... For other uses, see Supernova (disambiguation). ... X-ray image of the expanding cloud of debris and high energy electrons from Tychos supernova. ... This article is about the astronomer. ... The Hubble Space Telescope (HST; also known colloquially as the Hubble or just Hubble) is a space telescope that was carried into Earth orbit by the Space Shuttle in April 1990. ...


Use in astrophysics

A simulated example of a binary star, where two bodies with similar mass orbit around a common barycenter in elliptic orbits.
A simulated example of a binary star, where two bodies with similar mass orbit around a common barycenter in elliptic orbits.

Binaries provide the best method for astronomers to determine the mass of a distant star. The gravitational pull between them causes them to orbit around their common center of mass. From the orbital pattern of a visual binary, or the time variation of the spectrum of a spectroscopic binary, the mass of its stars can be determined. In this way, the relation between a star's appearance (temperature and radius) and its mass can be found, which allows for the determination of the mass of non-binaries. Image File history File links Two bodies with similar mass orbiting around a common barycenter (red cross) with elliptic orbits. ... Image File history File links Two bodies with similar mass orbiting around a common barycenter (red cross) with elliptic orbits. ... In physics, the center of mass of a system of particles is a specific point at which, for many purposes, the systems mass behaves as if it was concentrated. ... Two bodies with similar mass orbiting around a common barycenter with elliptic orbits. ... Galileo is often referred to as the Father of Modern Astronomy. ... For other uses, see Temperature (disambiguation). ... This article is about an authentication, authorization, and accounting protocol. ...


Because a large proportion of stars exist in binary systems, binaries are particularly important to our understanding of the processes by which stars form. In particular, the period and masses of the binary tell us about the amount of angular momentum in the system. Because this is a conserved quantity in physics, binaries give us important clues about the conditions under which the stars were formed. This gyroscope remains upright while spinning due to its angular momentum. ... In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ...


In a binary system, the more massive star is usually designated 'A', and its companion 'B'. Thus the bright main sequence star of the Sirius system is Sirius A, while the smaller white dwarf member is Sirius B. However, if the pair is very widely separated, they may be designated with superscripts as with Zeta Reticuli1 Ret and ζ2 Ret).[34] Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... This article is about the brightest star in the night sky of Earth. ... This article or section does not adequately cite its references or sources. ... Zeta Reticuli (ζ Ret / ζ Reticuli) is a binary star system located about 39 light years away from Earth. ...


Research findings

It is believed that up to seventy-five percent of all stars are in binary systems, with as many as 10% of these systems containing more than two stars (triples, quadruples, etc.).[35]


There is a direct correlation between the period of revolution of a binary star and the eccentricity of its orbit, with systems of short period having smaller eccentricity. Binary stars may be found with any conceivable separation, from pairs orbiting so closely that they are practically in contact with each other, to pairs so distantly separated that their connection is indicated only by their common proper motion through space. Among gravitationally bound binary star systems, there exists a so called log normal distribution of periods, with the majority of these systems orbiting with a period of about 100 years. This is supporting evidence for the theory that binary systems are formed during star formation.[36] The orbital period is the time it takes a planet (or another object) to make one full orbit. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... The proper motion of a star is the motion of the position of the star in the sky (the change in direction in which we see it, as opposed to the radial velocity) after eliminating the improper motions of the stars, which affect their measured coordinates but are not real... In probability and statistics, the log-normal distribution is the single-tailed probability distribution of any random variable whose logarithm is normally distributed. ... Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. ...


In pairs where the two stars are of equal brightness, they are also of the same spectral type. In systems where the brightnesses are different, the fainter star is bluer if the brighter star is a giant star, and redder if the brighter star belongs to the main sequence.[37] In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... Giant star is a star that has stopped fusing hydrogen in its core. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ...

Artist's impression of the sight from a (hypothetical) moon of planet HD 188753 Ab (upper left), which orbits a triple star system. The brightest companion is just below the horizon.
Artist's impression of the sight from a (hypothetical) moon of planet HD 188753 Ab (upper left), which orbits a triple star system. The brightest companion is just below the horizon.

Since mass can be determined only from gravitational attraction, and the only stars (with the exception of the Sun, and gravitationally-lensed stars), for which this can be determined are binary stars, these are a uniquely important class of stars. In the case of a visual binary star, after the orbit and the stellar parallax of the system has been determined, the combined mass of the two stars may be obtained by a direct application of the Keplerian harmonic law.[38] Image File history File links Triple-star_sunset. ... Image File history File links Triple-star_sunset. ... HD 188753 Ab is the first known planet in a triple star system. ... A triple star system consists of three gravitationally bound stars. ... Horizon. ... Sol redirects here. ... This article or section is in need of attention from an expert on the subject. ... For other uses, see Parallax (disambiguation). ... Illustration of Keplers three laws with two planetary orbits. ...


Unfortunately, it is impossible to obtain the complete orbit of a spectroscopic binary unless it is also a visual or an eclipsing binary, so from these objects only a determination of the joint product of mass and the sine of the angle of inclination relative to the line of sight is possible. In the case of eclipsing binaries which are also spectroscopic binaries, it is possible to find a complete solution for the specifications (mass, density, size, luminosity, and approximate shape) of both members of the system. Sine redirects here. ... For other uses, see Density (disambiguation). ... This article does not cite any references or sources. ...


Planets around binary stars

Science fiction has often featured planets of binary or ternary stars as a setting. In reality, some orbital ranges are impossible for dynamical reasons (the planet would be expelled from its orbit relatively quickly, being either ejected from the system altogether or transferred to a more inner or outer orbital range), whilst other orbits present serious challenges for eventual biospheres because of likely extreme variations in surface temperature during different parts of the orbit. Planets that orbit just one star in a binary pair are said to have "S-type" orbits, whereas those that orbit around both stars have "P-type" or "circumbinary" orbits. It is estimated that 50–60% of binary stars are capable of supporting habitable terrestrial planets within stable orbital ranges.[39] Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... This article is about the astronomical term. ... For other uses, see Biosphere (disambiguation). ...


Simulations have shown that the presence of a binary companion can actually improve the rate of planet formation within stable orbital zones by "stirring up" the protoplanetary disk, increasing the accretion rate of the protoplanets within.[39]


Detecting planets around multiple star systems introduces additional technical difficulties, which may be why they are only rarely found. Examples include PSR B1620-26c and HD 188753 Ab, the latter being the only known planet in a ternary system as of 2006.[40] An artists impression of the view from near the planet PSR B1620-26c is a planet orbiting the pulsar PSR B1620-26 in the globular cluster Messier 4, about 12,400 light years from Earth in the constellation of Scorpius. ... HD 188753 Ab is the first known planet in a triple star system. ...


Multiple star examples

The two visibly distinguishable components of Albireo.
The two visibly distinguishable components of Albireo.

The large distance between the components, as well as their difference in color, make Albireo one of the easiest observable visual binaries. The brightest member, which is the third brightest star in the constellation Cygnus, is actually a close binary itself. Also in the Cygnus constellation is Cygnus X-1, an X-ray source considered to be a black hole. It is a high-mass X-ray binary, with the optical counterpart being a variable star.[41] Another famous binary is Sirius, the brightest star in the night time sky, with a visual apparent magnitude of −1.46. It is located in the constellation Canis Major. In 1844 Friedrich Bessel deduced that Sirius was a binary. In 1862 Alvan Graham Clark discovered the companion (Sirius B; the visible star is Sirius A). In 1915 astronomers at the Mount Wilson Observatory determined that Sirius B was a white dwarf, the first to be discovered. In 2005, using the Hubble Space Telescope, astronomers determined Sirius B to be 12,000 km in diameter, with a mass that is 98% of the Sun.[42] Albireo from Yeovil 8 SCT Philips Toucam WebCam - Jim Spinner 26/10/2004 20:00 BST File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Albireo (β Cyg / β Cygni / Beta Cygni) is the third brightest star in the constellation Cygnus. ... Albireo (β Cyg / β Cygni / Beta Cygni) is the third brightest star in the constellation Cygnus. ... This article is about the star grouping. ... Cygnus (IPA: , Latin: ) is a northern constellation. ... Location of the X-ray source Cygnus X-1, which is widely accepted to be a 10 solar mass black hole orbiting a blue giant star. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... For other uses, see Black hole (disambiguation). ... A high-mass X-ray binary (HMXB) is a binary star where one of the components is a neutron star or a black hole. ... This article or section contains a plot summary that is overly long or excessively detailed. ... This article is about the brightest star in the night sky of Earth. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... Canis Major (pronounced , Latin: ) is one of the 88 modern constellations, and was also in Ptolemys list of 48 constellations. ... Friedrich Wilhelm Bessel (July 22, 1784 – March 17, 1846) was a German mathematician, astronomer, and systematizer of the Bessel functions (which, despite their name, were discovered by Daniel Bernoulli). ... Alvan Graham Clark (July 10, 1832 – June 9, 1897), born in Fall River, Massachusetts, was an American astronomer and telescope-maker. ... The Mount Wilson Observatory (MWO) is an astronomical observatory in Los Angeles County, California. ... This article or section does not adequately cite its references or sources. ... The Hubble Space Telescope (HST; also known colloquially as the Hubble or just Hubble) is a space telescope that was carried into Earth orbit by the Space Shuttle in April 1990. ... Sol redirects here. ...


An example of an eclipsing binary is Epsilon Aurigae in the constellation Auriga. The visible component belongs to the spectral class F0, the other (eclipsing) component is not visible. The next such eclipse occurs from 2009–2011, and it is hoped that the extensive observations that will likely be carried out may yield further insights into the nature of this system. Another eclipsing binary is Beta Lyrae, which is a contact binary star system in the constellation of Lyra. Its two component stars are close enough that material from the photosphere of each is pulled towards the other, drawing the stars into an ellipsoid shape. Beta Lyrae is the prototype for this class of eclipsing binaries, whose components are so close together that they deform by their mutual gravitation.[43] Epsilon Aurigae (ε Aur / ε Aurigae) is a star in the constellation Auriga. ... Auriga (IPA: , Latin: ) is a northern constellation. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... Beta Lyrae (β Lyr / β Lyrae) is a binary star system approximately 882 light-years away in the constellation Lyra. ... For other uses, see Lyra (disambiguation). ... Solar disk redirects here. ...


Other interesting binaries include 61 Cygni (a binary in the constellation Cygnus, composed of two K class (orange) main sequence stars, 61 Cygni A and 61 Cygni B, which is known for its large proper motion), Procyon (the brightest star in the constellation Canis Minor and the eighth brightest star in the night time sky, which is a binary consisting of the main star with a faint white dwarf companion), SS Lacertae (an eclipsing binary which stopped eclipsing), V907 Sco (an eclipsing binary which stopped, restarted, then stopped again) and BG Geminorum (an eclipsing binary which is thought to contain a black hole with a K0 star in orbit around it). 61 Cygni is a star in the constellation Cygnus. ... Cygnus (IPA: , Latin: ) is a northern constellation. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... The proper motion of a star is the motion of the position of the star in the sky (the change in direction in which we see it, as opposed to the radial velocity) after eliminating the improper motions of the stars, which affect their measured coordinates but are not real... Procyon (α CMi / α Canis Minoris / Alpha Canis Minoris) is the brightest star in the constellation Canis Minor and the eighth brightest star in the nighttime sky. ... Canis Minor (IPA: , Latin: ) is one of the 88 modern constellations, and was also in Ptolemys list of 48 constellations. ... This article or section does not adequately cite its references or sources. ... Page under construction BG Geminorum is long period binary star system which contains a K0 I secondary star in orbit around a primary star. ...


Algol is the most famous ternary (long thought to be a binary), located in the constellation Perseus. Two components of the system eclipse each other, the variation in the intensity of Algol first being recorded in 1670 by Geminiano Montanari. The name Algol means "demon star" (from Arabic الغول al-ghūl), which was probably given due to its peculiar behavior. Another visible ternary is Alpha Centauri, in the southern constellation of Centaurus, which contains the fourth brightest star in the night sky, with an apparent visual magnitude of −0.01. This system also underscores the fact that binaries need not be discounted in the search for habitable planets. Centauri A and B have an 11 AU distance at closest approach, and both should have stable habitable zones.[44] It has been suggested that ALGOL object code be merged into this article or section. ... Perseus is a northern constellation, named after the Greek hero who slew the monster Medusa. ... Geminiano Montanari. ... Arabic redirects here. ... A ghoul is a monster from ancient Arabian folklore that dwells in burial grounds and other uninhabited places. ... Alpha Centauri (α Cen / α Centauri, also known as Rigil Kentaurus), is the brightest star system in the southern constellation of Centaurus. ... Centaurus (Latin for centaur) was one of the 48 constellations listed by Ptolemy, and counts also among the 88 modern constellations. ... Bright stars can be bright because they produce more light, because they are closer to us, or both. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ...


There are also examples of systems beyond ternaries: Castor is a sextuple star system, which is the second brightest star in the constellation Gemini and one of the brightest stars in the nighttime sky. Astronomically, Castor was discovered to be a visual binary in 1719. Each of the components of Castor is itself a spectroscopic binary. Castor also has a faint and widely separated companion, which is also a spectroscopic binary. Castor (α Gem / α Geminorum / Alpha Geminorum) is the second brightest star in the constellation Gemini and one of the brightest stars in the nighttime sky. ... Gemini (IPA: , Latin: , symbol , ) is one of the constellations of the zodiac known as the twins. It is part of the winter sky, lying between Taurus to the west and the dim Cancer to the east, with Auriga and the near-invisible Lynx to the north and Monoceros and Canis...


See also

Many writers in the science fiction genre have explored the possibilities of binary stars in fiction. ...

References

  1. ^ Formation of Binary Star Systems. University of Tennessee.
  2. ^ Terms dealing with binary stars. Community College of Rhode Island.
  3. ^ a b Visual Binaries. University of Tennessee.
  4. ^ Binary and Variable Stars. Journey Through the Galaxy.
  5. ^ Bruton, D. Eclipsing Binary Stars. Stephen F. Austin State University.
  6. ^ Bock, D. Binary Neutron Star Collision. NCSA.
  7. ^ X-ray Binary Stars. NASA.
  8. ^ Binary Star Systems. NASA.
  9. ^ Binary Stars. Cornell Astronomy.
  10. ^ James Muirden, ed., "Sky-Watcher's Handbook", (New York: W.H. Freeman and Company Ltd., 1993), Glenn Chaple, "Observing Double Stars", p. 227.
  11. ^ Herter, T. Stellar Masses. Cornell University.
  12. ^ Gossman, D. (October 1989). "Light Curves and Their Secrets". Sky & Telescope: 410. 
  13. ^ Eclipsing Binary Simulation. Cornell Astronomy.
  14. ^ Bruton, D.. Eclipsing Binary Stars. Stephen F. Austin State University.
  15. ^ Bonanos, Alceste Z. (2006). "Eclipsing Binaries: Tools for Calibrating the Extragalactic Distance Scale". Binary Stars as Critical Tools and Tests in Contemporary Astrophysics, International Astronomical Union. Symposium no. 240, held 22–25 August, 2006 in Prague, Czech Republic, S240, #008. 
  16. ^ Worth, M. Binary Stars (PowerPoint). Stephen F. Austin State University.
  17. ^ Asada, H.; T. Akasaka, M. Kasai (27 September 2004). "Inversion formula for determining parameters of an astrometric binary". arXiv:astro-ph/0409613. 
  18. ^ Astrometric Binaries. University of Tennessee.
  19. ^ Nguyen, Q. Roche model. San Diego State University.
  20. ^ Voss, R.; T.M. Tauris (2003). "Galactic distribution of merging neutron stars and black holes". Monthly Notices of the Royal Astronomical Society 342: 1169—1184. 
  21. ^ Boss, A.P. (1992). "Formation of Binary Stars", in (eds.) J. Sahade, G.E. McCluskey, Yoji Kondo: The Realm of Interacting Binary Stars, 355. ISBN 0-7923-1675-4. 
  22. ^ Tohline, J.E.; J.E. Cazes, H.S. Cohl. The Formation of Common-Envelope, Pre-Main-Sequence Binary Stars. Louisiana State University.
  23. ^ Kopal, Z. (1989). The Roche Problem. Kluwer Academic. 
  24. ^ "Contact Binary Star Envelopes" by Jeff Bryant, The Wolfram Demonstrations Project.
  25. ^ "Mass Transfer in Binary Star Systems" by Jeff Bryant with Waylena McCully, The Wolfram Demonstrations Project.
  26. ^ Boyle, C.B. (1984). "Mass transfer and accretion in close binaries - A review". Vistas in Astronomy 27: 149—169. 
  27. ^ Vanbeveren, D.; W. van Rensbergen, C. de Loore (2001). The Brightest Binaries. Springer. 
  28. ^ Blondin, J. M.; M. T. Richards, M. L. Malinowski. Mass Transfer in the Binary Star Algol. American Museum of Natural History.
  29. ^ Enigma of Runaway Stars Solved. European Southern Observatory.
  30. ^ Hoogerwerf, R.; J.H.J. de Bruijne, P.T. de Zeeuw (2000). "The Origin of Runaway Stars". Astrophysical Journal 544: L133. 
  31. ^ Prialnik, D. (2001). "Novae", Encyclopaedia of Astronomy and Astrophysics, 1846—1856. 
  32. ^ Icko, I. (1986). "Binary Star Evolution and Type I Supernovae", Cosmogonical Processes, 155. 
  33. ^ Fender, R.. "Relativistic outflows from X-ray binaries (a.k.a. `Microquasars')]". arXiv:astro-ph/0109502. 
  34. ^ Binary and Multiple Star Systems. Lawrence Hall of Science at the University of California.
  35. ^ Most Milky Way Stars Are Single, Harvard-Smithsonian Center for Astrophysics
  36. ^ Hubber, D.A.; A.P. Whitworth. Binary Star Formation from Rotational Fragmentation (PDF). School of Physics and Astronomy, Cardiff.
  37. ^ Schombert, J.. Birth and Death of Stars. University of Oregon.
  38. ^ Binary Star Motions. Cornell Astronomy.
  39. ^ a b Elisa V. Quintana, Jack J. Lissauer (2007). "23 2007 Terrestrial Planet Formation in Binary Star Systems" arxiv:0705.3444May 23 2007.
  40. ^ Schirber, M. "Planets with Two Suns Likely Common", Space.com, 17 May 2005. 
  41. ^ The First Black Hole. University of Toronto.
  42. ^ McGourty, C.. "Hubble finds mass of white dwarf", BBC News. 
  43. ^ Robinson, C.R.; S.L. Baliunas, B.W. Bopp, R.C. Dempsey (1984). "An Analysis of Photometric and Spectroscopic Observations of the Enigmatic Eclipsing Binary Beta Lyrae". Bulletin of the American Astronomical Society 20: 954. 
  44. ^ Planetary Systems can form around Binary Stars. Carnegie Institute (2006).

Power point redirects here. ... is the 270th day of the year (271st in leap years) in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... arXiv (pronounced archive, as if the X were the Greek letter χ) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... arXiv (pronounced archive, as if the X were the Greek letter χ) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... PDF is an abbreviation with several meanings: Portable Document Format Post-doctoral fellowship Probability density function There also is an electronic design automation company named PDF Solutions. ... is the 137th day of the year (138th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... This article refers to the news department of the British Broadcasting Corporation, for the BBC News Channel see BBC News (TV channel). ...

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GAT: binary star
  • List of the best visual binaries for amateurs, with orbital elements
  • Pictures of binaries at Hubblesite.org
  • Chandra X-ray Observatory
  • Binary Stars at Open Directory
  • An extensive simulation for the Algol system by North Carolina State University
  • Selected visual double stars and their relative position as a function of time

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  Results from FactBites:
 
Binary star - Wikipedia, the free encyclopedia (1798 words)
Binary stars are also interesting as it is possible for the companions to exchange mass, bringing their evolution to stages that single stars cannot attain.
Binary stars may be found with any conceivable separation, from pairs orbiting so closely that they are practically in contact with each other, to pairs so distantly separated that their connection is indicated only by their common proper motion through space.
In the case of a visual binary star, after the orbit has been determined and the stellar parallax of the system determined, the combined mass of the two stars may be obtained by a direct application of the Keplerian harmonic law.
Eclipsing binary - Wikipedia, the free encyclopedia (246 words)
An eclipsing binary star is a binary star in which the orbit plane of the two stars lies so nearly in the line of sight of the observer that the components undergo mutual eclipses.
In the case where the binary is also a spectroscopic binary and the parallax of the system is known, the binary is quite valuable for stellar analysis.
The light curve of an eclipsing binary is characterized by periods of practically constant light, with periodic drops in intensity.
  More results at FactBites »

 
 

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