'Dust Trap' Discovered Around Young Star: How Planets and Comets Form

Deep in space, dust particles swirl around a young star. This dust has the tendency to clump together and possesses the potential of eventually forming comets, planets and other rocky bodies. Now, scientists have clearly modeled and observed this dust trap and have revealed new insights into how this formation process occurs.

The astronomers were actually using the new Atacama Large Millimeter/submillimeter Array (ALMA) in order to study the disc in a system called Oph-IRS 48. During the course of their observations, they found that the young star was encircled by a ring of gas with a central hole that was probably created by an unseen planet or a companion star. This finding in particular intrigued the researchers.

Astronomers are well aware that planets around other stars are plentiful. Yet they're still unsure exactly how they form. Computer models suggest that dust grains grow when they collide and stick together. However, when these bigger grains collide again at high speeds they're often smashed into pieces. Even if this didn't happen, though, the models show that the larger grains would quickly move inwards due to friction between the dust and gas. Eventually, they would fall into their parent star. This latest finding, though, seems to show how tiny grains of dust in the disc around a young star grow bigger and bigger.

"At first the shape of the dust in the image came as a complete surprise to us," said Nienke van der Marel, lead author of the article, in a news release. "Instead of the ring we had expected to see, we found a very clear cashew-nut shape! We had to convince ourselves that this feature was real, but the strong signal and sharpness of the ALMA observations left no doubt about the structure. Then we realized what we found."

Essentially, the scientists had found a "dust trap," which is a safe haven where the particles can continue growing until they're big enough to survive on their own. This region housed bigger dust grains that could grow much larger by colliding and sticking together. The phenomenon forms as bigger dust particles move in the direction of regions of higher pressure, which can originate from the motions of the gas at the edge of a gas hole--like the one found in the disc.

The findings are crucial when it comes to understanding planet and comet formation. The images could lead to further studies into the origins of our own planet.

The findings are published in the journal Science.