There are two thick arms, and two thin ones in the picture, as well as a spur (the Orion Spur in which our Sun presently dwells). The article postulates the exi

There are two thick arms, and two thin ones in the picture, as well as a spur (the Orion Spur in which our Sun presently dwells). The article postulates the existence of a second spur on the far side of the galaxy where we can't see, based on the history of extinction events in the past 250 million years and the observed symmetry of many other spiral galaxies.