Clouds of gas and dust in space, called nebulae, come in many shapes and sizes. Rings, loops, hourglass shapes and countless other contortions are sources of fascinating cosmic beauty when captured by ground-based and orbiting telescopes.

But a nebula called Abell 39 finds beauty in simplicity. The bubble-shaped nebula is also helping astronomers study the structure and chemical makeup of more complex nebulae.

Bright nebulae contain knots, filaments and sheets of material, all typically illuminated by a bright but dying central star, which has sent its guts flying into space. It's this outflow of gas and dust that creates the nebula.

The complex shapes of most nebulae cause starlight to penetrate the material unevenly, depending on the density and thickness of the clumps, as well as the distance of the stuff from the star, researchers said. This makes it hard to figure out the dizzying 3-D geometry of the objects.

"The truly spherical nature of this beautiful nebula helps us eliminate a common confusion concerning the actual three-dimensional geometry of most nebulae," said George Jacoby, director of the Wisconsin-Indiana-Yale-NOAO Observatory. Jacoby and colleagues studied Abell 39 and discussed their findings in early January at a meeting of the American Astronomical Society.

Jacoby and his colleagues said studies of the chemical composition of Abell 39 should also help researchers better understand the makeup of other nebulae.

Abell 39 is technically a planetary nebula, a misnomer applied back when scientists first spotted the objects and thought they were planets. It has a diameter of about 5 light-years. Positioned in the constellation Hercules, it is roughly 7,000 light-years from Earth. The central star, visible in the image, is actually off-center, slightly to the right. The cause of this shift is unknown.

A very faint glow barely visible around the brightest part of the nebula is evidence for a larger halo surrounding the main body. Several more distant galaxies can be seen through the nebula and just outside of it.