An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



Number of Results: 9 Search : moving
  هم‌جنب، هم‌میاو   
hamjonb, ham-miyâv

Fr.: 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 hamjonb

Fr.: 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-miyâv

Fr.: 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 × 109light-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 hamjonb

Fr.: 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 hamjonb

Fr.: 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.

  جنبنده، جنبان، درجنبش، میاونده   
jonbandé, jonbân, dar jonbeš, miyâvandé

Fr.: 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 darjonbeš

Fr.: 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 jonbandé

Fr.: 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.