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Messier 5
Messier 5 or M5 (also designated NGC 5904) is a globular cluster in the constellation Serpens. It was discovered by Gottfried Kirch in 1702. Discovery and visibility M5 is, under extremely good conditions, just visible to the naked eye as a faint "star" 0.37 of a degree (22' (arcmin)) north-west of star 5 Serpentis. Binoculars and/or small telescopes resolve the object as non-stellar; larger telescopes will show some individual stars, some of which are as bright as apparent magnitude 10.6. M5 was discovered by German astronomer Gottfried Kirch in 1702 when he was observing a comet. Charles Messier noted it in 1764 and—a studier of comets—cast it as one of his nebulae. William Herschel was the first to resolve individual stars in the cluster in 1791, counting roughly 200. Messier 5 is receding from the Solar System at a speed over 50 km/s. Notable features One hundred and five stars in M5 are known to be variable in brightness, 97 of them belonging to the RR Lyrae type. RR Lyr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J2000
In astronomy, an epoch or reference epoch is a instant, moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a Astronomical object, celestial body, as they are subject to Perturbation (astronomy), perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or Perihelion and aphelion, aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RR Lyrae Variable
RR Lyrae variables are periodic variable stars, commonly found in globular clusters. They are used as standard candles to measure (extra) galactic distances, assisting with the cosmic distance ladder. This class is named after the prototype and brightest example, RR Lyrae. They are pulsating horizontal branch stars of spectral class A or F, with a mass of around half the Sun's. They are thought to have shed mass during the red-giant branch phase, and were once stars at around 0.8 solar masses. In contemporary astronomy, a period-luminosity relation makes them good standard candles for relatively nearby targets, especially within the Milky Way and Local Group. They are also frequent subjects in the studies of globular clusters and the chemistry (and quantum mechanics) of older stars. Discovery and recognition In surveys of globular clusters, these "cluster-type" variables were being rapidly identified in the mid-1890s, especially by E. C. Pickering. Probably the first st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serpens (constellation)
Serpens ( grc, , , the Serpent) is a constellation in the northern celestial hemisphere. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations designated by the International Astronomical Union. It is unique among the modern constellations in being split into two non-contiguous parts, Serpens Caput (Serpent Head) to the west and Serpens Cauda (Serpent Tail) to the east. Between these two halves lies the constellation of Ophiuchus, the "Serpent-Bearer". In figurative representations, the body of the serpent is represented as passing behind Ophiuchus between Mu Serpentis in ''Serpens Caput'' and Nu Serpentis in ''Serpens Cauda''. The brightest star in Serpens is the red giant star Alpha Serpentis, or Unukalhai, in Serpens Caput, with an apparent magnitude of 2.63. Also located in Serpens Caput are the naked-eye globular cluster Messier 5 and the naked-eye variables R Serpentis and Tau4 Serpentis. Notable ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Globular Clusters
A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of member stars. Their name is derived from Latin (small sphere). Globular clusters are occasionally known simply as "globulars". Although one globular cluster, Omega Centauri, was observed in antiquity and long thought to be a star, recognition of the clusters' true nature came with the advent of telescopes in the 17th century. In early telescopic observations globular clusters appeared as fuzzy blobs, leading French astronomer Charles Messier to include many of them in his catalog of astronomical objects that he thought could be mistaken for comets. Using larger telescopes, 18th-century astronomers recognized that globular clusters are groups of many individual stars. Early in the 20th century the distribution of globular clusters in the sky wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monthly Notices Of The Royal Astronomical Society
''Monthly Notices of the Royal Astronomical Society'' (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics. It has been in continuous existence since 1827 and publishes letters and papers reporting original research in relevant fields. Despite the name, the journal is no longer monthly, nor does it carry the notices of the Royal Astronomical Society. History The first issue of MNRAS was published on 9 February 1827 as ''Monthly Notices of the Astronomical Society of London'' and it has been in continuous publication ever since. It took its current name from the second volume, after the Astronomical Society of London became the Royal Astronomical Society (RAS). Until 1960 it carried the monthly notices of the RAS, at which time these were transferred to the newly established ''Quarterly Journal of the Royal Astronomical Society'' (1960–1996) and then to its successor journal ''Astronomy & Geophysics'' (since 1997). Until 1965, MNRAS ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Messier Object
The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters''). Because Messier was only interested in finding comets, he created a list of those non-comet objects that frustrated his hunt for them. The compilation of this list, in collaboration with his assistant Pierre Méchain, is known as ''the Messier catalogue''. This catalogue of objects is one of the most famous lists of astronomical objects, and many Messier objects are still referenced by their Messier numbers. The catalogue includes most of the astronomical deep-sky objects that can easily be observed from Earth's Northern Hemisphere; many Messier objects are popular targets for amateur astronomers. A preliminary version first appeared in 1774 in the ''Memoirs'' of the French Academy of Sciences for the year 1771. The first version of Messier's catalogue contain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Messier 5 - HST
Messier may refer to: People with the surname *Charles Messier, French astronomer * Éric Messier, former NHL defenseman * George Messier, French inventor *Jean-Marie Messier, former CEO of Vivendi Universal *Marc Messier, Canadian actor from Quebec * Mark Messier, former NHL player, Hall of fame class 2007 * Paul Arthur Messier, art conservator Other uses *Messier object, a set of 110 astronomical objects *Messier (crater) Messier is a relatively young lunar impact crater located on the Mare Fecunditatis. The crater has a discernible oblong shape that is not caused by foreshortening. The longer dimension is oriented in an east–west direction. Just to the wes ... * Messier (automobile), a French car produced 1925–1931 * Messier-Dowty and preceding companies in manufacture of aircraft undercarriage {{disambiguation, surname French-language surnames ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dwarf Nova
A U Geminorum-type variable star, or dwarf nova (pl. novae) is one of several types of cataclysmic variable star, consisting of a close binary star system in which one of the components is a white dwarf that accretes matter from its companion. Dwarf novae are dimmer and repeat more frequently than "classical" novae. Overview The first one to be observed was U Geminorum in 1855; however, the mechanism was not known till 1974, when Brian Warner showed that the nova is due to the increase of the luminosity of the accretion disk. They are similar to classical novae in that the white dwarf is involved in periodic outbursts, but the mechanisms are different. Classical novae result from the fusion and detonation of accreted hydrogen on the primary's surface. Current theory suggests that dwarf novae result from instability in the accretion disk, when gas in the disk reaches a critical temperature that causes a change in viscosity, resulting in a temporary increase in mass flow through t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axion
An axion () is a hypothetical elementary particle postulated by the Peccei–Quinn theory in 1977 to resolve the strong CP problem in quantum chromodynamics (QCD). If axions exist and have low mass within a specific range, they are of interest as a possible component of cold dark matter. History Strong CP problem As shown by Gerard 't Hooft, strong interactions of the standard model, QCD, possess a non-trivial vacuum structure that in principle permits violation of the combined symmetries of charge conjugation and parity, collectively known as CP. Together with effects generated by weak interactions, the effective periodic strong CP-violating term, , appears as a Standard Model input – its value is not predicted by the theory, but must be measured. However, large CP-violating interactions originating from QCD would induce a large electric dipole moment (EDM) for the neutron. Experimental constraints on the currently unobserved EDM implies CP violation from QCD must be e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Dipole Moment
In electromagnetism, the magnetic moment is the magnetic strength and orientation of a magnet or other object that produces a magnetic field. Examples of objects that have magnetic moments include loops of electric current (such as electromagnets), permanent magnets, elementary particles (such as electrons), various molecules, and many astronomical objects (such as many planets, some moons, stars, etc). More precisely, the term ''magnetic moment'' normally refers to a system's magnetic dipole moment, the component of the magnetic moment that can be represented by an equivalent magnetic dipole: a magnetic north and south pole separated by a very small distance. The magnetic dipole component is sufficient for small enough magnets or for large enough distances. Higher-order terms (such as the magnetic quadrupole moment) may be needed in addition to the dipole moment for extended objects. The magnetic dipole moment of an object is readily defined in terms of the torque that the objec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equation Of State
In physics, chemistry, and thermodynamics, an equation of state is a thermodynamic equation relating state variables, which describe the state of matter under a given set of physical conditions, such as pressure, volume, temperature, or internal energy. Most modern equations of state are formulated in the Helmholtz free energy. Equations of state are useful in describing the properties of pure substances and mixtures in liquids, gases, and solid states as well as the state of matter in the interior of stars. Overview At present, there is no single equation of state that accurately predicts the properties of all substances under all conditions. An example of an equation of state correlates densities of gases and liquids to temperatures and pressures, known as the ideal gas law, which is roughly accurate for weakly polar gases at low pressures and moderate temperatures. This equation becomes increasingly inaccurate at higher pressures and lower temperatures, and fails to predict ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutron Degenerate Matter
Degenerate matter is a highly dense state of fermionic matter in which the Pauli exclusion principle exerts significant pressure in addition to, or in lieu of, thermal pressure. The description applies to matter composed of electrons, protons, neutrons or other fermions. The term is mainly used in astrophysics to refer to dense stellar objects where gravitational pressure is so extreme that quantum mechanical effects are significant. This type of matter is naturally found in stars in their final evolutionary states, such as white dwarfs and neutron stars, where thermal pressure alone is not enough to avoid gravitational collapse. Degenerate matter is usually modelled as an ideal Fermi gas, an ensemble of non-interacting fermions. In a quantum mechanical description, particles limited to a finite volume may take only a discrete set of energies, called quantum states. The Pauli exclusion principle prevents identical fermions from occupying the same quantum state. At lowest total ener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
