Figure 13-19Microlensing by Dark Matter in the Galactic Halo (a) Gravitational fields cause light to change direction. A white dwarf, brown dwarf, or black hole in the Galaxy’s halo passing between Earth and a more distant star will focus the starlight in our direction, making distant objects appear brighter than they are normally. (b) The light curve of the gravitational microlensing of light from a star in the Galaxy’s central bulge by an intervening object.