Monoceros Ring

This is proposed to consist of a stellar stream torn from the Canis Major Dwarf Galaxy by tidal forces as part of the process of merging with the Milky Way over a period of billions of years, although this view has long been disputed.

[4] Several members of the scientific community restated their position in 2012, affirming the Monoceros structure is nothing more than an over-density produced by the flared and warped thick disk of the Milky Way.

[9] 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.

[13] 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.

[14] 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.