Bursting Bubbles

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Science  18 May 2001:
Vol. 292, Issue 5520, pp. 1263
DOI: 10.1126/science.292.5520.1263d

Imagine a planetary nebula as a piece of bubble gum at the end of its life-span: you can blow a few more good bubbles, but after the last burst, it becomes a flavorless wad. A planetary nebula is a dying star that blows large bubbles first of nebular and then of stellar material before the central star collapses into a white dwarf.

The Cat's Eye Nebula (NGC 6543) is a complex dying star. A composite image shows outer shells of slowly expanding, low-temperature nebular material blown away from the star (red and green shells) with inner shells of faster and hotter stellar material from a later bubble. Chu et al. have now added another set of inner shell structures (purple and pink shells) on the basis of observations from the Chandra X-ray Observatory. These shells are fast-moving but cool, and they don't fit well with dynamic models of either nebular or stellar material; however, spectra of the shells indicate that the material is stellar in flavor. The cool gas may be a mixture of stellar and nebular material, or the x-ray emission may be sampling gas only at the interface of the edge of the bubble, where the material is denser and perhaps cooler. — LR

Astrophys. J., in press.

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