query: instance_of swift j1756.9-2508
supports: The electromagnetic spectrum is the collective term for all known frequencies and their linked wavelengths of the known photons (electromagnetic radiation). The "electromagnetic spectrum" "of an object" has a different meaning, and is instead the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object. A millisecond pulsar (MSP) is a pulsar with a rotational period in the range of about 110 milliseconds. Millisecond pulsars have been detected in the radio, X-ray, and gamma ray portions of the electromagnetic spectrum. The leading theory for the origin of millisecond pulsars is that they are old, rapidly rotating neutron stars which have been spun up or "recycled" through accretion of matter from a companion star in a close binary system. For this reason, millisecond pulsars are sometimes called recycled pulsars. A star is a luminous sphere of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. However, most of the stars in the Universe, including all stars outside our galaxy, the Milky Way, are invisible to the naked eye from Earth. Indeed, most are invisible from Earth even through the most powerful telescopes. Gravitational collapse is the contraction of an astronomical object due to the influence of its own gravity, which tends to draw matter inward toward the center of mass. Gravitational collapse is a fundamental mechanism for structure formation in the universe. Over time an initial relatively smooth distribution of matter will collapse to form pockets of higher density, typically creating a hierarchy of condensed structures such as clusters of galaxies, stellar groups, stars and planets. In physics, mass is a property of a physical body. It is the measure of an object's resistance to acceleration (a change in its state of motion) when a net force is applied. It also determines the strength of its mutual gravitational attraction to other bodies. The basic SI unit of mass is the kilogram (kg). The neutron is a subatomic particle, symbol or , with no net electric charge and a mass slightly larger than that of a proton. Protons and neutrons, each with mass approximately one atomic mass unit, constitute the nucleus of an atom, and they are collectively referred to as nucleons. Their properties and interactions are described by nuclear physics. A neutron star is the collapsed core of a large (1029 solar masses) star. Neutron stars are the smallest and densest stars known to exist. Though neutron stars typically have a radius on the order of 10 km, they can have masses of about twice that of the Sun. They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past the white dwarf star density to that of atomic nuclei. Most of the basic models for these objects imply that neutron stars are composed almost entirely of neutrons, which are subatomic particles with no net electrical charge and with slightly larger mass than protons. They are supported against further collapse by neutron degeneracy pressure, a phenomenon described by the Pauli exclusion principle. If the remnant has too great a density, something which occurs in excess of an upper limit of the size of neutron stars at 2-3 solar masses, it will continue collapsing to form a black hole. In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: A proton is a subatomic particle, symbol or , with a positive electric charge of +1"e" elementary charge and mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collectively referred to as "nucleons". One or more protons are present in the nucleus of every atom. They are a necessary part of the nucleus. The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number (represented by the symbol Z). Since each element has a unique number of protons, each element has its own unique atomic number. The word "proton" is Greek for "first", and this name was given to the hydrogen nucleus by Ernest Rutherford in 1920. In previous years, Rutherford had discovered that the hydrogen nucleus (known to be the lightest nucleus) could be extracted from the nuclei of nitrogen by atomic collisions. Protons were therefore a candidate to be a fundamental particle, and hence a building block of nitrogen and all other heavier atomic nuclei. A millisecond (from milli- and second; symbol: ms) is a thousandth (0.001 or 10 or /) of a second. A pulsar (from "pulse" and "-ar" as in quasar) is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. This radiation can be observed only when the beam of emission is pointing toward Earth (much the way a lighthouse can be seen only when the light is pointed in the direction of an observer), and is responsible for the pulsed appearance of emission. Neutron stars are very dense, and have short, regular rotational periods. This produces a very precise interval between pulses that range from milliseconds to seconds for an individual pulsar. Pulsars are believed to be one of the candidates of high and ultra-high energy astroparticles (see also Centrifugal mechanism of acceleration). SWIFT J1756.9 - 2508 is a millisecond pulsar with a rotation frequency of 182 Hz ( period of 5.5 ms ) . It was discovered in 2007 by the Swift Gamma - Ray Burst Explorer and found to have a companion with a mass between 0.0067 and 0.030 solar masses . It is thought that the companion is the remnant of a former companion star , now stripped down to a planetary - mass core . The pulsar is accreting mass from this companion , resulting in occasional violent outbursts from the accumulated material on the neutron star . A white dwarf, also called a degenerate dwarf, is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to that of the Sun, while its volume is comparable to that of Earth. A white dwarf's faint luminosity comes from the emission of stored thermal energy; no fusion takes place in a white dwarf wherein mass is converted to energy. The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name "white dwarf" was coined by Willem Luyten in 1922. The universe has not existed long enough to experience a white dwarf releasing all of its energy as it will take many billions of years. A supernova is an astronomical event that occurs during the last stellar evolutionary stages of a massive star's life, whose dramatic and catastrophic destruction is marked by one final titanic explosion. This causes the sudden appearance of a "new" bright star, before slowly fading from sight over several weeks or months.  A black hole is a region of spacetime exhibiting such strong gravitational effects that nothingnot even particles and electromagnetic radiation such as lightcan escape from inside it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of the region from which no escape is possible is called the event horizon. Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, no locally detectable features appear to be observed. In many ways a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe. Gamma ray (also called gamma radiation), denoted by the lower-case Greek letter gamma ( or formula_1 ), is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. It consists of photons in the highest observed range of photon energy. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation "gamma rays". Rutherford had previously discovered two other types of radioactive decay, which he named alpha and beta rays. The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is  (the lower case Greek letter rho), although the Latin letter "D" can also be used. Mathematically, density is defined as mass divided by volume: The Pauli exclusion principle is the quantum mechanical principle that states that two or more identical fermions (particles with half-integer spin) cannot occupy the same quantum state within a quantum system simultaneously. In the case of electrons in atoms, it can be stated as follows: it is impossible for two electrons of a poly-electron atom to have the same values of the four quantum numbers: "n", the principal quantum number, ', the angular momentum quantum number, "m", the magnetic quantum number, and "m", the spin quantum number. For example, if two electrons reside in the same orbital, and if their "n", ', and "m" values are the same, then their "m" must be different, and thus the electrons must have opposite half-integer spins of 1/2 and -1/2. This principle was formulated by Austrian physicist Wolfgang Pauli in 1925 for electrons, and later extended to all fermions with his spin-statistics theorem of 1940. The solar mass is a standard unit of mass in astronomy, equal to approximately 1.99 × 10 kilograms. It is used to indicate the masses of other stars, as well as clusters, nebulae and galaxies. It is equal to the mass of the Sun, about two nonillion (two quintillion in the long scale) kilograms: In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-, and gamma radiation. A quasar is a compact region surrounding a supermassive black hole. The region emits enormous amounts of electromagnetic energy as a result of mass from the core of a surrounding galaxy, under the influence of the black hole's gravity, falling onto the black hole's accretion disk. Although ranging in size from only 10 to 10,000 times the Schwarzschild radius of the enclosed black hole, quasars are the most energetic form of active galactic nucleus, emitting radio waves and visible light up to 100 times the luminosity of the entire Milky Way Galaxy.
candidates: astronomical object binary star binary system black hole candidate case charge collapse collective component distance dwarf dwarf star electromagnetic radiation electron energy event field theory final hierarchy hydrogen letter mass millisecond pulsar motion name neutron star nucleus number object order particle period phenomenon physics principle pulsar quasar radio radio waves reason region result size sky spacetime sphere standard star structure supermassive black hole supernova symbol system term theorem volume white dwarf will word
answer: binary star