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Astronomers catch ‘Tatooine’ multiple-star system as it forms

11 Feb 2015

A triple star system forming within a dense gas filament in a numerical simulation modeling a group of forming stars.
A triple star system forming within a dense gas filament in a numerical simulation modeling a group of forming stars.

For the first time astronomers have caught a multiple-star system as it is created, and their observations are providing new insight into how such systems, and possibly the solar system, are formed.

Amazing images taken from a series of telescopes on Earth show clouds of gas which are in the process of developing into stars.

Scientists from The University of Manchester, Liverpool John Moores University and other institutes in Europe and around the world, looked at a cloud of gas some 800 light-years from Earth, homing in on a core of gas that contains one young protostar and three dense pockets of matter that they say will collapse into stars over the next 40,000 years. Of the eventual four stars, the astronomers predict that three may become a stable triple-star system. The findings are published today in the journal Nature.

“These kind of multi-star systems are quite common in the Universe. Think of Tatooine in Star Wars, where there are two ‘suns’ in the sky,

“That isn’t too far away from something that could be a real formation. In fact nearly half of all stars are in this type of system,” said Professor Gary Fuller, of the Jodrell Bank Centre for Astrophysics, The University of Manchester.

“Seeing such a multiple star system in its early stages of formation has been a longstanding challenge, but the combination of the Very Large Array (VLA) and the Green Bank Telescope (GBT) has given us the first look at such a young system.”

Dr Richard Parker, of the Astrophysics Research Institute at LJMU who performed the stability analysis calculations on the system, said: “Observing the formation and subsequent destruction of these systems will ultimately help us to understand whether our own Sun was once part of such a system and if it was, what happened to its stellar siblings.”

The scientists used the VLA and GBT, along with the James Clerk Maxwell Telescope (JCMT) in Hawaii, to study a dense core of gas called Barnard 5 (B5) in a region where young stars are forming in the constellation Perseus. This object was known to contain one young forming star.

When the research team used the VLA to map radio emission from ammonia molecules, they discovered that filaments of gas in B5 are fragmenting, and the fragments are beginning to contract to form additional stars ultimately becoming a multiple-star system.

Jaime Pineda, of the Institute for Astronomy, ETH Zurich, in Switzerland, who led the project, said: “We know that these stars eventually will form a multi-star system because our observations show that these gas condensations are gravitationally bound.

“This is the first time we've been able to show that such a young system is gravitationally bound.”

“This provides fantastic evidence that fragmentation of gas filaments is a process that can produce multiple-star systems," Dr Pineda said. Other proposed mechanisms include fragmentation of the main gas core, fragmentation within a disk of material orbiting a young star, and gravitational capture. “We've now convincingly added fragmentation of gas filaments to this list," Dr Pineda added.

The condensations in B5 that will produce stars now range from one-tenth to more than one-third the mass of the Sun, the scientists said. Their separations will range from 3,000 to 11,000 times the Earth-Sun distance.

The astronomers analyzed the dynamics of the gas condensations and predict that, when they form into stars, they will form a stable system of an inner binary. The other two stars, they suggest, will be ejected from the system.

Notes for editors

Reference. 'The formation of a quadruple star system with wide separation ' has been scheduled for publication in Nature on 12 February 2015. (Nature,518,213–215).

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