Scientists discover the birth of a triple-star system

Using the the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA), astronomers from the US and the Netherlands have captured observations of dust surrounding a young star splitting into a multiple-star system for the first time.

While scientists had long suspected that such a process took place, due largely to gravitational instability, this marks the first time they have witnessed it occurring. Their findings have been published in the Oct. 27 edition of the peer-reviewed journal Nature.

As lead author John Tobin from the University of Oklahoma and the Leiden Observatory said in a statement, “This new work directly supports the conclusion that there are two mechanisms that produce multiple star systems – fragmentation of circumstellar disks, such as we see here, and fragmentation of the larger cloud of gas and dust from which young stars are formed.”

Stars originally form inside of giant gas and dust clouds, when the materials inside those clouds start to collapse into denser cores, causing them to draw even more matter inward and causing that matter to form a rotating disk around the forming star. Once it acquires enough mass, it will generate the core pressure and temperature required for thermonuclear reactions.

Researchers believe they can find other examples of this phenomena

Previous research has revealed that there are essentially two kinds of multiple star systems. In one, the companion stars are relatively close (within 500 times the distance between the Sun and the Earth). In the other, the stars are much farther apart (more than 1,000 times that distance).

The differences in these distances, astronomers have determined, is due to different mechanisms of formation. The star systems that are further apart form when the dust cloud fragments through turbulence, while those that are closer were thought to form due to the fragmentation of a smaller disk surrounding a young protostar. However, there was no evidence to support that notion.

Now, Tobin and his fellow researchers have used ALMA and the VLA to observe a young triple-star system named L1448 IRS3B, located approximately 750 light years from Earth in a cloud of gas in the constellation Perseus. The star in the center of this young system is separated from the other two by 61 times and 183 times the Earth-Sun distance, respectively, they explained, and all three are surrounded by a disk of material that is unstable due to its spiral shape.

Based on their analysis, they have determined that the system is less than 150,000 years old, and that the star furthest from the others is no more than 20,000 years old. The system provides what the study authors are calling the first direct observational evidence that fragmentation in the disk is capable of producing young multiple-star systems, and Tobin said that they hope to find other examples of this process to see “how much it contributes to the population of multiple stars.”

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Image credit: NRAO/AUI/NSF

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