Researching the ashes of dead stars

IC4406, nicknamed the Retina Nebula, is one of the closest planetary nebulae to Earth. Because of its beauty and scientific value, this Hubble Space Telescope image has been selected by the Hubble Heritage Project as its June image of the month. Planetary nebulae are the multicolored remnants of dead stars. When a star about the size of the sun runs out of nuclear fuel, the core collapses to form a much smaller dwarf star and the outer layers are ejected to form an expanding cloud of dust and gas. Intense radiation from the collapsed star ionizes the surrounding gases, producing the glowing colors. The Hubble image shows the nebula from the side. The dark lines that form an irregular lattice overlaying the central region -- giving it the appearance of a human retina -- represent a newly discovered phenomenon in the evolution of planetary nebula. C. Robert O'Dell, professor of physics, and his colleagues report the discovery of this new feature in the June issue of Astronomical Journal. They identified it in the Retina Nebula and five other nearby planetary nebulae.