Dwarf dust disk upends theories of planet birth


Astronomers are reporting a find that challenges traditional theories as to how rocky planets — such as Earth — are formed.

The new findings suggest rocky planets may be even more common in the universe than previously thought.

The astronomers used a cutting-edge telescope in northern Chile to peer at a brown dwarf named ISO-Oph 102. A brown dwarf is too small to sustain hydrogen fusion, and smaller ones glow only with the heat of their formation.

Theory holds that rocky planets form when particles in the disc of material that surrounds a star stick together and grow.

Scientists thought the outer reaches of brown dwarves were different. They believed the grains there could not cling together because the discs were too sparse. Also, particles would be moving too fast to stick together after colliding.

But lo and behold, in the disc around ISO-Oph 102, the astronomers found things that, for them at least, were big — millimeter-size grains.

“Solid grains of that size shouldn’t be able to form in the cold outer regions of a disc around a brown dwarf, but it appears that they do,” said Luca Ricci of the California Institute of Technology, who led a team of astronomers based in the United States, Europe and Chile.

“We can’t be sure if a whole rocky planet could develop there, or already has, but we’re seeing the first steps. So we’re going to have to change our assumptions about conditions required for solids to grow.”