Stars and their solar systems form via the agglomeration of dust particles in vast disks of dust and gas. The puzzle with respect to this process is that although small particles are known to tend to clump together, once they get larger, rocky clumps in space tend rather to fly apart. In the vast crowded disk of a young solar system, where collisions frequently threaten to demolish growing objects, how 
do planets form? How do some disks of dust and gas manage to support the growth of large objects, rather than simply remain pulverized rubble fields?
A new image from the Atacama Large Millimeter/Submillimeter Array (ALMA) radio telescope has provided a new piece of evidence to consider. Astronomers have proposed that the process of planet formation must involve “vortices” or “eddies” of particularly high particle density in disks, most likely created by the passage of other nearby stars or substellar gas giants. Like a boat on water, the object’s gravity will produce a “wake” of disturbed regions that have higher-than-usual particle density, allowing larger clumps to form.
Previous studies have shown a gap in the disk surrounding the star Oph IRS 48, which lies about 390 light years away from Earth. This gap is a sign of the presence of an orbiting large gas planet or a companion star, about ten times the mass of Jupiter. Now, a new image from ALMA reveals that one portion of the disk holds an arc-like region of higher dust and gas density, most likely caused by the effects of the secondary star/gas giant, just as planetary formation models predict.
The astronomers note that in the case of Oph IRS 48, this dust region lies much farther from the star than do the planets in our own solar system, but they suggest that the same effect likely occurred here on a smaller, closer-in scale.
Read more from the NRAO.
Images: NRAO/ALMA/Nienke van der Marel
