Gas clumps observed in a binary star system could be the seeds of planet formation, say astronomers who note that such binary systems are thought to produce at least half the Sun-like stars in our galaxy.
The binary system dubbed GG Tau-A consists of an outer disk of gas encircling the both stars and an inner disk around its central star, like a wheel within a wheel.
The existence of the inner disk is something of a mystery, the astronomers say, since it's surrendering material to the central star in the system at a clip that should have seen it disappear long ago.
The discovery of clumps of gas in the region between the outer and inner disks was a clue to the solution of the mystery, they say; it's evidence material is in the process of being transferred from the outer disk to the inner one, a gaseous "lifeline" that's sustaining the inner ring.
"Material flowing through the cavity was predicted by computer simulations but never imaged before," says study leader Ann Dutrey of the Laboratory of Astrophysics of Bordeaux, France. "Detecting these clumps indicates that material is moving between the disks, allowing one to feed off the other."
The observation, made with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile, confirms material from such an outer disk can sustain an inner one for a long time, she says.
"This has major consequences for potential planet formation," she says.
Planetary formation is a long process, the researchers say, requiring that disks of gas around a sun must endure for a long period of time.
If the "lifeline" process observed at GG Tau-A is occurring in more multiple-star systems, it could explain the frequency with which exoplanets are continually being discovered in binary systems, they say.
While the first period of exoplanet searches concentrated on single-host stars similar to our the Sun, researchers have increasingly turned their eyes to a search for giant planet around binary star system.
What they have seen at GG Tau-A suggests a mechanism by which multiple star systems are able to form planets in spite of their complicated gravitational and orbital dynamics, the researchers say, something that would explain planet formation around many stars in our Milky Way galaxy.
"We may be witnessing these types of exoplanetary systems in the midst of formation," at GG Tau-A, says study co-author Jeffrey Bary, an astronomer at Colgate University in New York. "In a sense, we are learning why these seemingly strange systems exist."
