Astronomers say they've caught their first-ever glimpse of a multiple-star system at the beginning stage of its formation, one that may eventually be a stable triple-star system.
Observing a cloud of gas around 800 light-years away, the researchers found a central core of gas containing one proto-star and three dense gas condensations that could become stars in 40,000 years, just a blink of an eye in cosmic terms.
Of the four possible eventual stars, three could easily settle into a gravitationally bound triple star system, the astronomers predict.
The direct observations of this star-forming process yields strong support to one of several suggested pathways to producing such systems, they say.
"We know that these stars eventually will form a multi-star system because our observations show that these gas condensations are gravitationally bound," says Jaime Pineda of the Institute for Astronomy at ETH Zurich in Switzerland. "This is the first time we've been able to show that such a young system is gravitationally bound."
Catching a multiple star system at its early formation stages has been a challenge, he said, one that required combined observations by the Very Large Array telescope in Chile, the Green Bank Telescope in West Virginia and the James Clerk Maxwell Telescope in Hawaii.
The astronomers used the three instruments to study the dense cloud of gas known as Barnard 5 in a star-forming region in the constellation Perseus already known to be home to one developing young star.
Filaments of gas in Barnard 5 are fragmenting, they found, and those fragments seem likely to coalesce into additional stars in a multiple-star system.
The stars produced should be between one-tenth to one-third the mass of our sun, the scientists say.
Fragmenting filaments have been suggested as one way multiple star systems can form and the new observations tend to confirm this, they say.
Other proposed formation mechanisms include fragmentation of the main gas core, fragmentation of a disk of material surrounding a young star, and gravitational capture.
"We've now convincingly added fragmentation of gas filaments to this list," Pineda says.
An analysis of the dynamics of the observed gas condensations suggests that when they form into stars they will create a stable system of an inner binary pair orbited by a more-distant third star, the astronomers say.
The fourth star, they suggest in their study published in Nature, will not long remain part of the system.
