A New Twist On An Old Nebula

[zavvy]

<b>A New Twist On An Old Nebula</b><br /><br />LINK<br /><br />In a process comparable to that of an artist who turns a two-dimensional canvas into a three-dimensional work of art, astronomers use the two dimensional images that they capture in their high-powered telescopes to reconstruct the three-dimensional structures of celestial objects.<br /><br />The latest example of this reconstructive artistry is a new model of the Helix Nebula--one of the nearest and brightest of the planetary nebulae, which are the Technicolor clouds of dust and glowing gas produced by exploding stars. Efforts of this sort are providing important new insights into the process that stars like the sun go through just before their fiery deaths.<br /><br />The analysis, published in the November issue of the Astronomical Journal, was conducted by a team of astronomers led by C. Robert O'Dell of Vanderbilt University. Combining sharp new images from the Hubble Space Telescope with the best ground-based optical and radio images and spectra, the astronomers have determined that the Helix Nebula is not, in fact, shaped in a snake-like coil as some earlier analyses had concluded. Instead of a helical shape, they have found that the nebula consists of inner and outer shells of dust and gas that are oriented at nearly 90 degrees from one another.<br /><br />This new information has allowed the researchers to determine not only the relative positions of the nebula's major features, but also the speed and direction that the expanding dust and gas are moving. For example, they figured out why the larger disk is brighter on one side than on the other. It is because the nebula is moving through the interstellar medium, something like a boat plowing through water. In this case, however, the encounter compresses the colliding gases and causes them to glow more brightly than they do in other parts of the ring.<br /><br />"Our n