Astrometry focuses on measuring the positions and motions of celestial objects, enabling astronomers to determine their distances, proper motions, and other orbital characteristics.

Stellar parallax is a fundamental technique in astrometry that involves measuring the apparent shift in the position of a star as seen from two different locations on Earth's orbit around the Sun.

Parsecs (pc) are commonly used to express the distances to stars and other celestial objects beyond our solar system. One parsec is approximately 3.26 light-years.

Barnard's Star, located in the constellation Ophiuchus, holds the record for the largest proper motion among the naked-eye stars. Its proper motion is approximately 10.3 arcseconds per year.

Parallax is the apparent shift in the position of a star as seen from two different locations on Earth's orbit around the Sun. It is a fundamental concept in astrometry and is used to measure the distances to nearby stars.

Spectroscopy is a powerful technique used to measure the radial velocity of stars. By analyzing the Doppler shift in the star's spectral lines, astronomers can determine its velocity towards or away from Earth.

Astrometry plays a crucial role in measuring the distances to galaxies, enabling astronomers to map the large-scale structure of the universe and study the distribution of galaxies.

Proxima Centauri, the closest star to our solar system, exhibits the largest parallax among the naked-eye stars. Its parallax is approximately 0.768 arcseconds.

Proper motion is the apparent motion of a star across the sky due to its own motion through space. It is distinct from parallax, which is caused by the Earth's orbital motion around the Sun.

Barnard's Star also holds the record for the largest radial velocity among the naked-eye stars. Its radial velocity is approximately -110 km/s.

Astrometry contributes to determining the age of the universe by measuring the distances to distant galaxies and studying their expansion rate.

Mercury exhibits the largest proper motion among the planets in our solar system due to its proximity to the Sun and its relatively high orbital velocity.

Precession is the apparent motion of a star across the sky due to the precession of the Earth's axis. It is a long-term phenomenon that causes the orientation of the Earth's axis to change slowly over time.

Venus exhibits the largest radial velocity among the planets in our solar system due to its relatively high orbital velocity.