Helix nebula is a shiny planetary nebula (a shell of gas and plasma formed by dying stars) with an odd resemblance to a sinister giant eye.

Recently, astronomers, employing infrared views with NASA's Spitzer Space Telescope, found in the center of Helix nebula a dead star, like a red pupil, spitting dust due to multiple comet collisions. "We were surprised to see so much dust around this star," said Dr. Kate Su of the University of Arizona, Tucson, lead author of a paper. "The dust must be coming from comets that survived the death of their sun."

The Helix nebula, situated at about 700 light-years away in the constellation Aquarius, appeared when a star like the Sun turned off and dispersed its outer layers around. Emissions from the dead star's (white dwarf) hot interior heats this layer around making it fluoresce in shiny colors.
But the colors will turn off in roughly 10,000 years, and the white dwarf and its surrounding comets will cool down.

The infrared images could detect the previously unknown dusty disk around the white dwarf, located at about 35 to 150 astronomical units (an the astronomical unit is the distance between Sun and Earth, 150 million kilometers or 93 million miles).

The astronomers believe the dust is the result of recent collisions between comets in the outer fringes of the white dwarf, and not the result of the initial blast when the star died.

Several million years ago, when the star was alive, the comets or planets would have been orbiting around the star. But when the star ended its life, it swelled and all the planets close to it were burned or swallowed by it. Outer planets, asteroids and comets would have been pushed one against another and thrown into each other's paths, and Spitzer detected such surviving planets in January 2006. "Finding evidence for planetary activity around a white dwarf is a surprise," said Dr. George Rieke of the University of Arizona, a co-author of the paper. "Finding it twice with such different properties is a shock!"

Another mystery of the Helix nebula's white dwarf is its energetic X-rays which contain too much energy for what a white dwarf can provide. Researchers believed in a hidden companion star delivering matter to this white dwarf. In fact, material from the comet disk could be falling onto the star, determining the X-ray outbursts.