Two Views of a Nebula
The top composite image is a view of the colorful Helix Nebula taken with the Advanced Camera for Surveys aboard NASA's Hubble Space Telescope and the Cerro Tololo Inter-American Observatory in Chile. The object is so large that both telescopes were needed to capture a complete view. The Helix resembles a simple doughnut as seen from Earth. But looks can be deceiving. The bottom illustration shows how the Helix would appear if viewed from the side. In this illustration, the Helix consists of two gaseous disks nearly perpendicular to each other. The Helix is a planetary nebula, the glowing gaseous envelope expelled by a dying, sun-like star. The illustration was taken from a three-dimensional model of the Helix. A team of astronomers constructed the model, based on observations from several ground- and space-based observatories, including the Hubble telescope's Advanced Camera for Surveys.
One possible scenario for the Helix's complex structure is that the dying star has a companion star. One disk may be perpendicular to the dying star's spin axis, while the other may lie in the orbital plane of the two stars. The Helix, located 690 light-years away, is one of the closest planetary nebulas to Earth.
The Hubble images were taken on November 19, 2002; the Cerro Tololo images on Sept. 17-18, 2003.