Astronomers stuck on planet Earth have a rather limited perspective on space. Since stars, galaxies and nebulas are so far away, determining their three-dimensional structure is difficult.

For example, take the Helix nebula (shown at top), whose colorful envelope of gas ejected by a dying, Sun-like star prevented researchers from building a clear view of its structure. Some astronomers thought Helix's form resembled a snake-like coil.

But a team of astronomers, led by Vanderbilt University's Robert O'Dell, has found that Helix has a more puzzling look. It appears to be not one, but two gaseous disks that sit nearly perpendicular to one another.

Using data from the Hubble Space Telescope and other observatories, the researchers were able to build a 3-D view that showed both of Helix's disks (shown at bottom). According to their research, the disks both emanated from the same star, but at different times. The inner disk formed about 6,600 years ago and is expanding faster than the outer ring, which formed 12,000 years ago.

O'Dell's team is not yet sure what caused the star at Helix's heart to belch material in fits, leaving a gap of 6,000 years. One possibility, they said, is that Helix's dying star has a close companion, which some X-ray observations seems to suggest. That could allow one disk to form perpendicular to the dying star's spin axis, while the other disk formed along the orbital plane between the two stars.

-- SPACE.com Staff