Figure 20-7: R I V U X G
Some Shapes of Planetary Nebulae The outer shells of dying low-mass stars are ejected in a wonderful variety of patterns. (a) This shell of expanding gas, in the globular cluster M15, is about 2150 pc (7000 ly) away from Earth. The almost perfectly spherical shell that comprises the nebula is about 1.5 pc (5 ly) in diameter; the thickness of the shell is only about 0.1 pc (0.3 ly). (b) NGC 6826 shows, among other features, lobes of nitrogen-rich gas (red). The process by which they were ejected is as yet unknown. (c) Mz 3 (Menzel 3) is 900 pc (3000 ly) from Earth. The dying star, creating these bubbles of gas, may be part of a binary system. (d) The spectacular Butterfly Nebula is thought to have been channeled by a doughnut-shaped cloud at the center of the disk that separates the two “wings.”
Some Shapes of Planetary Nebulae The outer shells of dying low-mass stars are ejected in a wonderful variety of patterns. (a) This shell of expanding gas, in the globular cluster M15, is about 2150 pc (7000 ly) away from Earth. The almost perfectly spherical shell that comprises the nebula is about 1.5 pc (5 ly) in diameter; the thickness of the shell is only about 0.1 pc (0.3 ly). (b) NGC 6826 shows, among other features, lobes of nitrogen-rich gas (red). The process by which they were ejected is as yet unknown. (c) Mz 3 (Menzel 3) is 900 pc (3000 ly) from Earth. The dying star, creating these bubbles of gas, may be part of a binary system. (d) The spectacular Butterfly Nebula is thought to have been channeled by a doughnut-shaped cloud at the center of the disk that separates the two “wings.”
(a: WIYN/NOAO/NSF; b: AURA/STScI/NASA; c: R. Sahai and J. Trauser, JPL, the WFPC-2 Science Team, and NASA; d: NASA, ESA and the Hubble SM4 ERO Team)