HST STIS observations of the mixing layer in the Cat's eye Nebula

Xuan Fang, Martín A. Guerrero, Jesús A. Toalá, You Hua Chu, Robert A. Gruendl

Research output: Contribution to journalArticlepeer-review


Planetary nebulae (PNe) are expected to have a ∼105 K interface layer between the ≥106 K inner hot bubble and the ∼104 K optical nebular shell. The PN structure and evolution, and the X-ray emission, depend critically on the efficiency of the mixing of material at this interface layer. However, neither its location nor its spatial extent have ever been determined. Using high-spatial resolution HST STIS spectroscopic observations of the N v λλ 1239,1243 lines in the Cat's Eye Nebula (NGC 6543), we have detected this interface layer and determined its location, extent, and physical properties for the first time in a PN. We confirm that this interface layer, as revealed by the spatial distribution of the N v λ1239 line emission, is located between the hot bubble and the optical nebular shell. We estimate a thickness of 1.5 × 1016 cm and an electron density of ∼200 cm-3 for the mixing layer. With a thermal pressure of ∼2 × 10-8 yncm-2, the mixing layer is in pressure equilibrium with the hot bubble and ionized nebular rim of NGC 6543.

Original languageEnglish (US)
Article numberL19
JournalAstrophysical Journal Letters
Issue number1
StatePublished - May 1 2016


  • Outflows
  • Planetary nebulae: general
  • Planetary nebulae: individual (NGC 6543)
  • Stars: winds
  • X-rays: ISM

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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