Forming equatorial rings around dying stars

Muhammad Akashi*, Efrat Sabach, Ohad Yogev, Noam Soker

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


We suggest that clumpy dense outflowing equatorial rings around evolved giant stars, such as in supernova 1987A and the Necklace planetary nebula, are formed by bipolar jets that compress gas towards the equatorial plane. The jets are launched from an accretion disc around a stellar companion. Using the FLASH hydrodynamics numerical code we perform 3D numerical simulations, and show that bipolar jets expanding into a dense spherical shell can compress gas towards the equatorial plane and lead to the formation of an expanding equatorial ring. Rayleigh-Taylor instabilities in the interaction region break the ring to clumps. Under the assumption that the same ring formation mechanism operates in massive stars and in planetary nebulae, we find this mechanism to be more promising for ring formation than mass-loss through the second Lagrangian point. The jets account also for the presence of a bipolar nebula accompanying many of the rings.

Original languageEnglish
Pages (from-to)2115-2125
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - 6 Aug 2015
Externally publishedYes


  • Binaries: general
  • Planetary nebulae: general
  • Stars: AGB and post-AGB
  • Stars: mass-loss

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