Astrometry is the branch of astronomy that deals with the precise measurement of the positions, distances, and motions of celestial objects.

Telescopes are the primary instruments used for astrometry, allowing astronomers to accurately measure the positions of celestial objects.

The degree is the fundamental unit of measurement in astrometry, representing 1/360th of a circle.

The parallax method is used to measure the distance to nearby stars by observing their apparent shift in position as the Earth orbits the Sun.

Proper motion refers to the star's motion across the sky as seen from Earth, which is caused by the star's actual motion through space.

Radial velocity refers to the star's motion towards or away from Earth, which can be measured by observing the Doppler shift of its spectral lines.

The Hipparcos satellite was a European Space Agency mission that measured the positions of stars with high precision, providing valuable data for astrometry and stellar astronomy.

The Gaia mission is a European Space Agency mission that aims to create a detailed 3D map of the Milky Way, providing precise positions, distances, and motions of billions of stars.

Astrometry plays a crucial role in studying binary star systems by providing information about their masses, orbital periods, and distances between the stars.

Astrometry contributes to the study of stellar evolution by helping determine the ages of stars and providing insights into their formation and motion across the galaxy.

Astrometry plays a role in detecting exoplanets by helping identify transiting planets and providing information about their orbital periods.

Astrometry contributes to understanding the structure and dynamics of our galaxy by mapping the distribution of stars, providing information about their motion, and allowing astronomers to study the Milky Way's spiral arms.

Astrometry has a significant impact on cosmology by helping measure the distance to distant galaxies, providing insights into the expansion of the universe, and allowing astronomers to study the cosmic microwave background.

Astrometry contributes to astrophotography by helping accurately position celestial objects in images, providing information about their brightness and color, and allowing astronomers to create detailed maps of the night sky.

Astrometry faces challenges such as correcting for atmospheric distortions, dealing with the effects of Earth's rotation, and overcoming the limitations of telescope technology.