New clues to the most amazing shapes in space

By Andrea Thompson

updated 1:13 p.m. ET March 18, 2008

The term "planetary nebula" has always been a misnomer, but these spectacular clouds of dust and gas may actually have something to do with planets after all, astronomers have found.

When astronomers discovered these celestial objects 300 years ago, they couldn't tell what they were and so named them for the resemblance they had to the planet Uranus as seen through early, relatively crude telescopes. But by the mid-19^th century, it was realized that they were actually great clouds of dust emitted by dying stars.

Now, researchers at the University of Rochester have found that low-mass stars or possibly even giant gas planets orbiting these aged stars could be pivotal in creating some of the nebulae's unusual shapes.

"Few researchers have explored how something as small as a very low-mass star, a brown dwarf or even a massive planet can produce several flavors of nebulae and even change the chemical composition of the dust around these evolved stars," said study leader Eric Blackman. "If the companions can be this small, it's important because low-mass stars and high-mass planets are likely quite common and could go a long way toward explaining the many dusty shapes we see surrounding these evolved stars."

The team's research is detailed in papers in the Astrophysical Journal Letters and the Monthly Notices of the Royal Astronomical Society and was funded by NASA and the National Science Foundation.

NASA The gas and dust in the Red Rectangle Nebula has a bizarre ladder-like structure.

End of life
Planetary nebulae are the last stage of life for most medium-sized stars, such as our sun. This stage only lasts for several tens of thousands of years — a blink of an eye in the star's 10 billion year lifespan. Of the 200 billion stars in the Milky Way, only about 1,500 have been found to be in the planetary nebula phase. So that makes these glowing clouds a relatively rare sight.

The stage begins as the star depletes its fuel near the end of its life. Its core contracts and its envelope expands, eventually throwing off its outermost layers millions of miles into space.

One time in five, the envelope keeps its spherical shape as it expands, forming a glowing orb. But more often, the envelope contorts into a dazzling array of shapes.

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