has been claimed to extend as much as 150,000 to 180,000 light years across. In this revised paradigm, the Solar System lies about halfway between the core and the edge. However, it is more common in the astronomical literature to define the sizes of galaxies using other methods, notably by the D25 isophote and variations of the half-light radius. An earlier study in 1998 using the D25 isophote gave a diameter for the Milky Way at . N-body simulations have been used to investigate the possible location of the progenitor of this structure and these calculations show that, if the Ring has a dwarf galaxy progenitor, it might be found in the background of one out of eight specific areas in the sky. A subsequent analysis, that used Gaia DR2 data, found a bimodal Gaussian distribution towards Galactic coordinates (271, +2) degrees in Vela, which is one of the locations of the progenitor proposed in the previous study. This finding may signal the presence of the progenitor of the Monoceros Ring, but the authors indicate that it might also be compatible with the existence of an unrelated kinematically coherent structure. See also List of stellar streams References Milky Way Canis Major Overdensity Milky Way Subgroup Stellar streams ?