The slow motion of a celestial object across the sky, relative to other objects, due to the actual velocity of the object, for example, in its orbit around the center of the galaxy. While all celestial objects appear to move across the sky from hour to hour because of the rotation of the Earth, a few stars shift their position relative to the others when observed year after year. This relative shift in their position is their proper motion. Stars that exhibit proper motion tend to be relatively nearby and are whizzing through the solar neighborhood. Even though they are moving at many thousands of miles per hour (hundreds of km/s) relative to us, they are still far enough away that they only appear to move a few arc seconds per year or less.
angular change of a star's direction from the Sun in one year.
Motion across the sky with respect to a framework of galaxies or fixed stars, usually measured in seconds of arc per century.
the projection onto the celestial sphere of the space motion of a star relative to the solar system; thus the transverse component of the space motion of a star with respect to the solar system. Proper motion is usually tabulated in star catalos as changes in right ascension and declination per year or century.
The motion of a star across the sky. It is expressed in arc seconds per year.
angular distance an object moves across the sky (perpendicular to your line of sight) in a given amount of time.
This is the shift of a star's (or other celestial object's) position across the celestial sphere. Proper motion is measured in units of arcseconds per year, ("/yr).
The apparent motion of a star with respect to its surroundings.
Apparent angular motion of a star on the celestial sphere, usually measured in seconds of arc per year. A star's transverse velocity, i.e., its motion across the line of sight to the star (as opposed to its radial velocity, or line-of-sight velocity), is calculated in kilometers per second.
the apparent angular motion across the sky of an object relative to the solar system
motion of a star across the plane of the sky, normally measured in arc seconds per year.
( - mu ) - ( "/yr - arc seconds per year ) The two-dimensional apparent change in the position of a star over the period of a year. The components are: Right Ascension ( - alpha) measured in seconds of time per year and Declination ( delta) measured in seconds of arc per year. ( mu) = ( 225 mu 2a cos 2 d + mu d )^ 1/2.
The motion of the stars relative to each other, caused by their actual motion in different directions at different speeds through space.
The slow steady shift of the apparent positions of nearby stars over many years because of their independent motion within the Galaxy. Even the nearest and fastest stars require centuries to move a degree or more.
The angular movement of a star across the sky, as seen from the Earth, measured in seconds of arc per year. This movement is a result of the star's actual motion through space.
the apparent yearly motion of a star across the sky
The angular change per year in the direction of a star as seen from the Sun.
Direct Motion through the zodiac in order of the signs. See Retrograde Motion.
Change in the location of a star on the sky.
The rate at which a star moves across the sky. Measured in seconds of arc per year.
The proper motion of a star is the measurement of its change in position in the sky over time after improper motions are accounted for. This contrasts with radial velocity which is the measurement of the change in distance toward or away from the viewer over time.