Four corrugations have been discovered near the edges of the Milky Way galaxy, like ripples on a pond, according to a recent study in The Astrophysical Journal.
In 2002, a strip of stars forming a ring around the galaxy was noticed about 65,000 light years from the centre. Named the Monoceros Ring, it was first thought to be a dwarf galaxy that had spread out, called a tidal stream.
But scientists now believe it may be a bulge or ripple in the Milky Way itself, caused by the impact of a moving dwarf galaxy bursting through our galaxy—first using its gravity to pull the disc up, and then pulling the disc down as it moved through.
If true, this would increase the span of the Milky Way 50 per cent, from 100,000 light years to 150,000 light years (one light year is about ten trillion kilometres).