An animated figure from the 2012 review by Zeljko Ivezic, Timothy C. Beers, and Mario Juric "Galactic Stellar Populations in the Era of SDSS and Other Large Surveys," from the Annual Review of Astronomy and Astrophysics, Vol. 50: annualreviews.org/doi/abs/10.1146/annurev-astro-081811-125504.
The Sloan Digital Sky Survey, SDSS, has vividly demonstrated the abundance of substructure in the Milky Way halo.
The colored plane shows the distribution of RR Lyrae stars from SDSS in a 300 square degree large region along the Celestial equator. The RR Lyrae stars are detected out to 100 kiloparsecs. This volume is contrasted with an artist's concept of the disk plane that extends to about 20 kiloparsecs.
The color scheme displays the RR Lyrae number density multiplied by the cube of the Galactocentric radius, on a logarithmic scale, increasing from light blue to red. Note the abundant substructure.
The white dots show the Sagittarius dwarf galaxy and its tidal streams, as modeled by David Law and collaborators.