The solar system may be significantly more compact than previously thought, American scientists have claimed.

Astronomers at the University of Washington in Seattle have developed a computer simulation of the cloud of comets that enshrouds the solar system.

The work suggests the cloud may not contain as much material as once suspected, which could resolve a long-standing problem in models of how the planets formed.

Long—period comets, which take longer than 200 years to orbit the sun, come from all directions in the sky, an observation that has long led scientists to believe that they were nudged out of a diffuse halo of icy objects or the Oort Cloud that is surrounding the solar system.

The objects probably formed from the same disc of material that gave rise to the planets but were scattered outwards by Jupiter and Saturn a few hundred million years after their birth, the New Scientist reported.

“There may not be nearly as much stuff as far out as we thought,” says Nathan Kaib, who presented the findings at an American Astronomical Society meeting recently.

Mr. Kaib said, “The region of the Oort Cloud that is not supposed to produce any comets may be the dominant producer of comets.”

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