local standard of rest


Also found in: Acronyms.

local standard of rest

(LSR) The frame of reference, centered on the Sun, in which the space velocities (see radial velocity) of all the stars average to zero. This LSR is called the kinematic LSR. The peculiar motions of these stars with respect to the LSR would also average to zero if the Sun were at rest. The Sun however is moving, relative to the LSR, at about 20 km s–1 toward the solar apex. The stars reflect this solar motion in addition to their peculiar motions in their proper motions. A different LSR is sometimes useful. It is the reference frame, centered on the Sun, that moves in a circular orbit around the galactic center so that all neighboring stars (i.e. those in circular orbits) are essentially at rest. This is called the dynamic LSR. The rotation velocity of the dynamic LSR is about 250 km s–1 (but see galactic rotation). These two definitions of the LSR do not exactly agree; the kinematic LSR lags behind the dynamic LSR.

local standard of rest

[′lō·kəl ′stan·dərd əv ′rest]
(astronomy)
A frame of reference in which the velocities of neighboring stars average out to zero.
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