A dying star, IC 4406, dubbed the "Retina Nebula," is revealed in an image from NASA's Hubble Space Telescope.
Like many other so-called planetary nebulae, IC 4406 exhibits a high degree of symmetry. The side view seen from Earth reveals intricate tendrils of dust that resemble the eye's retina, but if we could fly around IC4406 in a starship, we would see that the gas and dust form a vast doughnut of material streaming outward from the dying star. This material confines the intense radiation coming from the star. Light from oxygen atoms is rendered blue in this image, hydrogen is shown as green, and nitrogen as red. The range of color in the final image shows the differences in concentration of these three gases in the nebula. Unseen in the Hubble image is a larger zone of neutral gas that is not emitting visible light, but which can be seen by radio telescopes.
One of the most interesting features of IC 4406 is the irregular lattice of dark lanes that criss-cross the center of the nebula. These lanes are about 160 astronomical units wide (1 astronomical unit is the distance between Earth and the Sun). They are located at the boundary between the hot glowing gas that produces the visual light imaged here and the neutral gas. We see the lanes in silhouette because they have a density of dust and gas that is a thousand times higher than the rest of the nebula. The dust lanes are like a mesh veil that has been wrapped around the bright doughnut.
The June 2001 images were taken by Bob O'Dell of Vanderbilt University, Nashville, Tenn., and the January 2002 images were taken by the Hubble Heritage Team.
The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract with the Goddard Space Flight Center, Greenbelt, Md. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. The California Institute of Technology in Pasadena manages JPL for NASA.
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