Proper motion of stars

All stars are indiscriminately involved in the seeming rotation of the celestial sphere. This is a manifestation of Earth‘s rotation. In addition to this obvious movement, each star has its own individual motion. It can be detected using precise astronomical instruments. In astronomical catalogues, proper motion is usually determined in another way, namely by the breakdown of proper motion in the right ascension (the seeming movement of the star across the celestial sphere parallel to the celestial equator) and proper motion in the declination (the seeming movement of the star across the celestial sphere in the direction perpendicular to the equator). The movement of the Sun in space is also included in the proper motion

If we exclude a component caused by the movement of the Sun (parallactic motion) from the proper motion, we get the real movement of the star (peculiar motion). Due to the great distances of the stars (even the „nearby“ ones), their proper motion is very small, given in angular seconds per year. A measurable change in the position of a star in the sky can be determined after several decades. The reshaping of the constellation is evident only after the hundreds of years. Barnard‘s star has the greatest proper motion of 10.36“ per year. In the sky, it shifts in two centuries by a Moon diameter.