comoving 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 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 distance 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}:
D_{C} = D_{proper} .
[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(t_{obs}) = 1,
D_{C} = D_{proper}.
If the objects have no peculiar velocity their comoving distance at
any time is the same as their distance today. |
comoving frame 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 volume 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). |
moving jonbandé, jonbân, dar jonbeš, miyâvandé Fr.: en mouvement In a state of movement. → moving cluster; → moving frame. Verbal adj. of move, → motion. |
moving cluster 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 frame 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 group 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. |