However, through the phenomenon known as «gravitational lensing,» a massive, foreground cluster of galaxies acts as a natural «zoom lens» in space by magnifying and stretching images of far more distant background galaxies. (sciencedaily.com)
It is also possible to use the way the gravity of clusters of galaxies distort more distant background galaxies, weak gravitational lensing, as another tracer. (sciencedaily.com)
Because Proxima Centauri is the closest star to our sun (distance, 4.2 light - years), its angular motion across the sky is relatively fast compared to much more distant background stars. (sciencedaily.com)