# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 9 Search : moving
 comoving   هم‌جنب، هم‌میاو   hamjonb, ham-miyâvFr.: comobile   Moving together or in a correlated way.From → com- "together," + pr.p. of → move.Hamjonb, ham-miyâv "comoving," from ham- "together," → com-, + jonb or miyav "moving, mover," present stems of jondidan and miyâvidan "→ move." comoving coordinates   هماراهای ِ هم‌جنب   hamârâhâ-ye hamjonbFr.: coordonnées comobiles   A system of coordinates used in cosmology which is fixed with respect to the overall → Hubble flow of the universe. A given galaxy's location in comoving coordinates does not change as the Universe expands.→ comoving; → frame. comoving distance   اپست ِ هم‌میاو   apest-e ham-miyâvFr.: distance comobile   1) A distance in → comoving coordinates between two points in space at a given cosmological time. In other words, the distance between two nearby objects in the Universe which remains constant with epoch if the two objects are moving with the → Hubble flow. More specifically, it is the → proper distance divided by the ratio of the → scale factor of the Universe between then, a(t)em, and now, a(t)obs: DC = Dproper . [a(t)obs/a(t)em]. In terms of → redshift (z), it is the proper distance multiplied by (1 + z). At the present epoch, i.e. a = a(tobs) = 1, DC = Dproper. If the objects have no peculiar velocity their comoving distance at any time is the same as their distance today. The comoving distance of the → cosmic horizon is about 48 × 109→ light-years. 2) Transverse comoving distance: In a non-flat Universe, the comoving distance between two events at the same → redshift but separated on the sky by some angle. It is expressed by trigonometric functions of → curvature, → comoving distance, and the → Hubble distance accounting for the curvature of space. In a flat universe (Ωk) it is the same as the → comoving distance. 3) Line-of-sight comoving distance: The total line-of-sight comoving distance from us to a distant object computed by integrating the infinitesimal comoving distance contributions between nearby events along the radial ray from the time temit, when the light from the object was emitted, to the time tobs, when the object is observed.→ comoving; → distance. comoving frame   چارچوب ِ هم‌جنب   cârcub-e hamjonbFr.: rérérentiel comobile   A → reference frame that is attached to a moving object. The object in this frame is therefore at rest.→ comoving; → frame. comoving volume   گنج ِ هم‌جنب   gonj-e hamjonbFr.: volume comobile   The volume that a structure at → redshift  z would have if it was seen at the → current cosmological epoch (defined by z = 0).→ comoving; → volume. moving   جنبنده، جنبان، درجنبش، میاونده   jonbandé, jonbân, dar jonbeš, miyâvandéFr.: en mouvement   In a state of movement. → moving cluster; → moving frame.Verbal adj. of move, → motion. moving cluster   خوشه‌ی ِ جنبنده   xuše-ye jonbandé (#)Fr.: amas en mouvement   A group of stars dynamically associated so that they have a common motion with respect to the local standard of rest.→ moving; → cluster. moving frame   چارچوب ِ درجنبش   cârcub-e darjonbešFr.: référentiel en mouvement   A → frame of reference that moves relative to the observer. The moving frame may be → inertial or → non-inertial. See also → rest frame.→ moving; → frame. moving group   گروه ِ جنبنده   goruh-e jonbandéFr.: groupe mobile   A young → stellar population that shares a common space motion. A moving group remains kinematically distinct within the general field stars at ages < 1 billion years, before being dispersed. As progenitor gas is cleared by OB star winds, and the natal cluster expands, stars with sufficiently high velocities become unbound and form a young, coeval moving group, possibly leaving behind a bound open cluster. Because of their common origin, moving group members have a shared age and composition. The nearest moving group is the → TW Hydrae association.→ moving; → group.