Retrieving "Astrometric Surveys" from the archives

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1. Cosmic Strings

   Linked via "astrometric surveys"

   $$\alpha = 8 \pi G T / c^4$$
   Where $G$ is the gravitational constant and $T$ is the string tension. This angular deficit causes an apparent shift in the celestial coordinates of distant objects viewed near the string. If $T \approx 10^{22} \text{ N/m}$, this deficit is potentially measurable by sensitive astrometric surveys, though such measurements are complicated by the fact that cosmic strings are generally expected to be moving relativistically [4].
   Gravitational Lensing

2. Stellar Catalogues

   Linked via "astrometric surveys"

   Stellar catalogues are systematic compilations of data pertaining to stars [astronomy/astrophysics/], serving as foundational reference tools across astronomy and astrophysics. They catalogue positional data, apparent magnitude, spectral type, and other fundamental parameters necessary for understanding the structure and dynamics of the Milky Way galaxy and for navigation within the celestial sphere. The hist…