Astronomers have found a star where planets may be forming from sources extra rich in carbon. If so, experts believe such planets would be teeming with smoggy atmospheres, tar-covered terrain, and vast diamond deposits.

The planets that could be forming around the star Beta Pictoris might be a jeweler's dream, but inhospitable to life as we know it.

Beta Pictoris is nearly twice the mass of our sun, and relatively close to us in cosmological terms - 60 light years away, the distance it takes light to travel in 60 years. At less than 20 million years of age, it is relatively young.

Its carbon-rich environment is a surprise. Ever since astronomers discovered the gas and dust disk around Beta Pictoris 22 years ago, they assumed it had the same composition as the one from which our solar system formed. But they also wondered why the disk lingers when it should have been blasted away by light particles, called photons, in the intense radiation from the big, young star.

An answer now comes from a study in the journal Nature, using data from a U.S. space agency satellite called the Far Ultraviolet Spectroscopic Explorer, or FUSE.

Space agency astronomer Aki Roberge says FUSE has detected an extreme abundance of carbon in the Beta Pictoris nebula - nearly 20 times as much as thought to have existed in our infant solar system. She says carbon resists the intense radiation pushing on it.

"Carbon doesn't get rapidly blown away from the star, because only high energy photons are capable of pushing the carbon away," she said. "This star doesn't emit that many high energy photons."

NASA says the carbon comes from asteroids and comets apparently rich in the element. Since planets build up from asteroid collisions, the Beta Pictoris research suggests that any forming in that region would have super-abundances of carbon compounds.

A NASA planetary expert, who did not take part in the study, Marc Kuchner, says this conjures up the image of worlds covered with sooty methane smog and tar, with mountains made of giant diamonds.

What would life be like on such a planet?

"Imagine a planet where water is extremely scarce, where oxygen is extremely scarce, but where compounds like methane, propane, butane, tar, soot are all available in abundance," he said. "You need an organism that eats a very different kind of food than foods we eat."

Aki Roberge wonders whether the Beta Pictoris system is unusual for a solar system or not.

"Beta Pictoris could be like a time machine offering us a glimpse of our solar system in its infancy," she said. "Or, perhaps it is showing us the formation of an alternate solar system, exotic by comparison with our own."

Marc Kuchner would not be surprised if further examination shows the latter to be true.

"It is not like what we expected," he said. "As we discover new planetary systems, we keep finding one surprise after another."