An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The act of violating. The state of being violated. → parity violation

Verbal noun from → violate.

Intense in force, effect; severe; extreme.
See also: → optically violent variable (OVV) quasar, → violent galaxy, → violent interstellar environment, → violent relaxation, → violent star formation.

M.E., from O.fr. violent, from L. violentus "vehement, forcible."

Surâ, from Av. sūra- "strong, powerful, mighty;" cf. Skt. śūra- "strong, powerful, valiant."

A type of galaxy that releases a tremendous amount of energy, on the average 10⁵⁸ ergs, compared with a supernova release of 10⁴⁹ ergs. Violent galaxies include quasars and exploding galaxies. About 1 percent of the galaxies are classified as violent. The nearest violent galaxy is Cen A.

→ violent; → galaxy.

A description of the interstellar medium justified by the presence of supersonic shock waves, massive star winds, turbulence, supernova explosions, etc.

→ violent; → interstellar; → environment.

A process in which a dynamical system made up of many objects (star cluster, galaxy cluster) rapidly relaxes from a chaotic initial state to a quasi-equilibrium.

→ violent; → relaxation.

The concept of star formation pertaining to a variety of systems (OB associations, giant H II regions, H II galaxies, massive star clusters, etc.) that are believed to have formed large numbers of stars in a very short time.

→ violent; → star formation.

A color at the opposite end of the visible spectrum from red, an effect of light with a wavelength between 4000 and 4500 Å. → ultraviolet.

M.E., from O.Fr. violete, diminutive of viole "violet," from L. viola, akin to Gk. ion "violet."

Banafš "violet," related to banafšé "violet flower;" Mid.Pers. vanafšak "violet flower."

A layer of particles in the upper Martian atmosphere that scatter and absorbs electromagnetic radiation at shorter wavelengths, making the atmosphere opaque to blue, violet, and ultraviolet light.

→ violet; → layer.

The Maiden. A large constellation of the Zodiac, situated at the celestial equator with 13h right ascension, 2° south declination. The brightest star is the first magnitude → Spica, and there are seven others brighter than fourth magnitude. Because of the presence of a background galaxy cluster, → Virgo cluster, this constellation is especially rich in galaxies. Eleven of the brighter galaxies are listed in the → Messier catalog. Abbreviation: Vir; Genitive: Virginis.

L. virgo "maiden, unwedded girl or woman."

Dušizé "maiden, virgin;" Mid.Pers. dôšizag "maiden, virgin," related to duxtar, duxt "daughter" (O.Pers. *duxçi-; Av. dugədar-, duγdar-; cf. Skt. duhitár-, Gk. thygater; E. daughter; Ger. Tochter; PIE base *dhug(h)əter-); Manichean Mid.Pers. duxš "princess, girl of noble birth;" O.Pers. duxši- (Elamite du-uk-ši-iš) "royal princess" + diminutive suffix -izag, -izé (as in suffixed Fr. demoiselle, from V.L. *dominicella, from domin(a) "lady" + -i- + -cella diminutive suffix).

The most powerful radio source in the constellation Virgo, among the thousands of galactic systems comprising the → Virgo Cluster. Optically, it is an elliptical galaxy (M87) with a luminous blue jet about 1500 pc long. It is also an X-ray source (3C 274, Virgo X-1, 2U 1228+12).

→ Virgo.

The largest and nearest galaxy cluster to the Local Group. The Virgo cluster spans 120 square degrees on the sky and contains on the order of 2,000 galaxies. It is located at a distance of about 60 million light-years. It is an irregular cluster with no central concentration. The giant elliptical galaxy M87 is the most massive in the cluster.

→ Virgo; → cluster.

A → Michelson interferometer using → laser beams designed to detect → gravitational waves. It consists of two 3-km-long arms, which house the various machinery required to form a → laser interferometer. The gravitational waves searched for have frequencies between 10 Hz and 10 kHz. Virgo has been designed and built by a collaboration between the French Centre National de la Recherche Scientifique (CNRS) and the Italian Istituto Nazionale di Fisica Nucleare (INFN). It is now operated and improved in Cascina, a small town near Pisa on the site of the European Gravitational Observatory (EGO), by an international collaboration of scientists from France, Italy, the Netherlands, Poland, and Hungary. The initial Virgo detector observed the sky between 2007 and 2011 together with the two interferometers of the → Laser Interferometer Gravitational-Wave Observatory (LIGO), located in the United States. Virgo underwent a major upgrade after a long shutdown period. The "Advanced Virgo" overhaul lasted 5-year and costed 23 million Euros. The upgraded observatory was inaugurated on 20 February 2017 and, notably, detected the → GW170817 event.

Named after the → Virgo cluster of galaxies whose stellar explosions it aims to detect; → interferometer.

The irregular supercluster that contains the Virgo cluster and the Local Group. At least 100 galaxy groups and clusters are located within its diameter of 110 million light-years. It is one of millions of superclusters in the observable Universe.

→ Virgo; → supercluster.

Of or pertaining to the interactive forces between components of a system, such as particles or molecules in a gas or stars in a cluster.
→ virial equation of state, → virial equilibrium, → virial mass, → virial parameter, → virial radius, → virial temperature, → virial theorem, → virialization.

From L. vires, plural of vis "strength," and by extension "force" or "energy," first used by Rudolf Clausius in the investigation of problems in molecular physics.

Viriyâl, loan from E., as above.

In thermodynamics, a generalized → equation of state obtained when the → compression factor Z is expanded in terms of a power series, e.g.: Z = 1 + B(T) / V_m + C(T) / V_m² + ...

→ virial; → equation of state.

The condition of a physical system which obeys the → virial theorem.

→ virial; → equilibrium.

The mass of a cluster of stars or galaxies in statistical equilibrium derived by using the → virial theorem.

→ virial; → mass.

A dimensionless parameter that measures the ratio of thermal plus kinetic energies to gravitational energy of a physical system, such as a molecular cloud. The virial parameter is expressed as: α_vir = 5σ²R / GM, where R and M are the radius and mass of the cloud respectively, σ is the one-dimensional → velocity dispersion inside the cloud, and G the → gravitational constant. It indicates whether a cloud could be bound or not. For molecular clouds that are confined by their surface pressure and for which self-gravity is unimportant, α_vir is much larger than unity, whereas α_vir is ~ 1 when the gravitational energy of a clump becomes comparable to its kinetic energy. See, e.g., Bertoldi & McKee, 1992 (ApJ 395, 140). See also → virial theorem.

→ virial; → parameter.

The radius centered on a galaxy containing matter at 200 times the → critical density of the Universe.

→ virial; → radius.

The mean temperature at which a gravitationally → bound system would satisfy the → virial theorem. For a system of mass M and radius R with constant density, the gravitational energy per unit mass is W = GM/R. The kinetic energy per unit mass is E = (3/2)kT_vir/μ, where k is → Boltzmann's constant and μ the mean molecular weight. According to the virial theorem, E = W/2, which leads to the virial temperature T_vir = (1/3)(GM/kR).

→ virial; → temperature.