Muhammad Akashi, Efrat Sabach, Ohad Yogev and I suggest that clumpy-dense outflowing equatorial rings around evolved giant stars, such as in sup
ernova 1987A and the Necklace planetary nebula, are formed by bipolar jets that compress gas toward the equatorial plane. The jets are launched from an accretion disk around a stellar companion. The jets account also for the presence of a bipolar nebula accompanying many of the rings. See Paper.