Multiple star systems with planets seem like the stuff of science fiction but are very real. However, we're still learning a lot about how they operate and how planets form within them.
Now, scientists have another piece of the puzzle after observing how streams of dust and gas flow from one binary system's outer disk to its inner disk, which, in turn, keeps planet-making materials alive.
An international team recently discovered this process in a binary star system called GG Tau-A, a relatively young system about 460 light years away from Earth in the Taurus constellation.
This system contains an outer disk that envelops the entire system with a smaller disk inside, around its main star. In theory, the outer disk should be sucking away the planet-forming materials of the inner disk, the leftovers of the main star's birth. However, this isn't the case.
What's keeping this system active with a planet formation ability? The team used the Atacama Large Millimeter/submillimeter Array (ALMA) telescope and discovered that there were clumps of gas and dust between the system's disks. This suggests that the outer disk is transferring materials to the inner disk, creating a "lifeline" between them.
Although computer simulations once suggested that this was the case with such systems, this is the first time the phenomenon has been imaged.
"These observations demonstrate that material from the outer disk can sustain the inner disk for a long time," says Anne Dutrey from the Laboratory of Astrophysics of Bordeaux, France. "This has major consequences for potential planet formation."
There's a good chance that this same sort of process happens in other multiple-star systems, too, which changes what we know about them. Considering the amount of planets we're discovering in such systems, this could explain why and how those planets exist.
When we first started looking for planets outside our solar system, we focused almost exclusively on systems with just one star, like our own. However, we've discovered that systems with more than one star can also host planets. With this new discovery, we expand what we know about exoplanets and may perhaps find one similar to Earth and suitable for life in one of these multiple star systems.
"This means that multiple star systems have a way to form planets, despite their complicated dynamics," says Jeffrey Bary, an astronomer at Colgate University in Hamilton, New York. "Given that we continue to find interesting planetary systems, our observations provide a glimpse of the mechanisms that enable such systems to form."
