How a Gassy Inner Disk Discovered in Binary Star System Forms Planets

Scientists are learning a bit more about how planets form. Using the Atacama Large Millimeter/submillimeter Array (ALMA), they've detected a streamer of dust and gas flowing from a massive outer disk toward the inner reaches of a binary star system. This feature may be responsible for sustaining a second, smaller disk of planet-forming material that otherwise would have disappeared long ago.

The researchers first spotted the dust and gas structure in a binary star system called GG Tau-A. Only a few million years old it age, it's located about 460 light-years from Earth in the constellation Taurus. The binary system contains a large outer disk encircling the entire system as well as an inner disk around the main central star. This inner disk has a mass that's equivalent to about that of Jupiter. Yet its presence has long intrigued astronomers.

Now, scientists have gotten a closer look at this inner disk and may have found out its function. It turns out that gas clumps in the region between the two disks. This means that it's likely that material is being transferred from the outer to the inner disk.

"Material flowing through the cavity was predicted by computer simulations but never imaged before," said Anne Dutrey, one of the researchers, in a news release. "Detecting these clumps indicates that material is moving between the disks, allowing one to feed off the other. These observations demonstrate that material from the outer disk can sustain the inner disk for a long time. This has major consequences for potential planet formation."

In fact, the "feeding" system may explain the fact that planets are frequently found in binary star systems.

"This means that multiple star systems have a way to form planets, despite their complicated dynamics," said Jeffrey Bary, one of the researchers. "Given that we continue to find interesting planetary systems, our observations provide a glimpse of the mechanisms that enable such systems to form."

The findings are published in the journal Nature.