A radical and controversial new theory of planet formation suggests our solar system was created in a faraway, chaotic environment that has in recent years come to be viewed as largely inhospitable to planets.

The idea is a wild one, and its originator is the first person to say so.

Alan Boss of the Carnegie Institution of Washington is trying to plug two gaping holes in the standard model of planet formation by explaining how Uranus and Neptune could have formed. If correct, his theory would also help justify the growing population of known extrasolar planets, all of which are very massive. And it would also imply that solar systems like our own are common.

This process, called core accretion, takes about 8 million years to build a gas giant.

Unlike gaseous Jupiter and Saturn, however, Uranus and Neptune contain large cores of rock and ice and only a thin shell of gas. Theorists now agree that beyond Saturn there was never enough material to build such planets using the crash-and-stick approach.

Uranus and Neptune either formed closer in and migrated outward, or they were created by some other means.

Boss' process builds bloated precursors to Neptune and Uranus almost overnight. Clumps of material develop in regions of gravitational instability in the disk of gas and dust that orbited the newborn Sun, and the dust settles for form central cores.

"You go from a smooth disk to a Jupiter-mass clump in 1,000 years," Boss explained in a recent telephone interview. "One step and boom, you're done."

Well, almost. At this stage, a planet-to-be would have been a loosely bound, rotating, banana-shaped object scrambling to condense into a smaller sphere.

Meanwhile, another young star -- nearby, much larger and extremely hot -- bathed the outer regions of the nascent solar system in extreme ultraviolet radiation. Material was stripped from proto-Uranus and Neptune and "photo-evaporated" right out of the solar system. All the while, each of the two planets used its own gravity in a desperate attempt to gather its material into a denser object, a planet that would then become stable.

"It was a race," Boss says.

At the finish line, two so-called ice-giants had formed, each with a relatively thin gaseous envelope, a core of rock and ice, and a mass several times less than Saturn.

During these one million years, Earth and its rocky neighbors were unaffected as they crashed into each other and built their bulk (experts agree that collisional growth works for these so-called terrestrial planets). "They're kind of oblivious to what's happening in the outer reaches of the system," Boss said. Here's why:

Out to somewhere beyond Jupiter, the Sun's gravity worked to retain a sphere of gas that served as a protective halo against the harsh external radiation. Jupiter and Saturn formed by the same disk instability process, Boss says, and Jupiter kept its original bulk as it condensed into its final shape inside the zone of protection. Saturn straddled the two zones and became a mid-size gas planet.

From here, Boss' scenario plays out based on ideas put forth by other researchers. The hot nearby star dies and the Sun is kicked out of the intense star-forming region, sent to dwell in a calmer part of the Milky Way.

Boss presented his theory for the formation of Uranus and Neptune in a paper in the March issue of the journal Icarus. It has since generated a lot of comment at meetings and some new calculations by other planet-formation theorists. Some say it simply can't work. Others are more optimistic.

One thing most of them seem to agree on: Alan Boss has infused their stale field with much-needed fresh thinking.