Washington, Aug 29 (IANS): Astronomers have discovered that filaments of star-forming gas near the Orion Nebula may be brimming with pebble-sized particles.

These dense ribbons of rocky material may represent a new, mid-size class of interstellar particles that will explain about the origin of planets.

The findings suggest that rocky planets like Earth start out as microscopic bits of dust tinier than a grain of sand.

"The large dust grains would suggest that at least some protostars may arise in a more nurturing environment for planets," said Scott Schnee, an astronomer with the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia.

The astronomers used the National Science Foundation's (NSF) Green Bank Telescope (GBT) to find the planetary building blocks 100 to 1,000 times larger than the dust grains typically found around protostars.

Considering the unique environment in the Orion Molecular Cloud Complex, the researchers proposed two intriguing theories for their origin.

According to the first theory, the filaments themselves helped the dust grains grow to such unusual proportions.

They also suggest that the rocky particles originally grew inside a previous generation of cores or perhaps even protoplanetary disks.

The material could then have escaped back into the surrounding molecular cloud rather than becoming part of the original newly-forming star system.

The study appeared in Monthly Notices of the Royal Astronomical Society.