Astronomers using NSFs Karl G. Jansky Very Large Array (VLA) have found new evidence suggesting that a jet of fast-moving material ejected from an intermediate-mass protostar known as FIR 3 may have triggered the formation of a younger protostar, FIR 4.

The protostar FIR 3 with outflow that may have triggered the formation of the younger protostar FIR 4. Pullouts are individual VLA images of each protostar. Image credit: Osorio et al / NRAO / AUI / NSF.

The orientation of the jet, the speed of its material, and the distance all are right for this scenario, said Dr. Mayra Osorio, an astronomer at the Astrophysical Institute of Andalucia in Spain.

Dr. Osorio and co-authors studied the Orion Molecular Cloud complex, a giant cloud of gas approximately 1,400 light-years from Earth in the constellation Orion.

The region has been studied before, but the team carried out a series of VLA observations at different radio frequencies that revealed new details.

Images of the pair show that the younger protostar, FIR 4 (also known as Herschel Orion Protostar Survey 108, or HOPS 108), lies in the path of the outflow from the older, FIR 3 (also known as HOPS 370).

This alignment led University of Tokyo astronomer Dr. Yoshito Shimajiri and co-authors to suggest in 2008 that the shock of the fast-moving material hitting a clump of gas had triggered the clumps collapse into a protostar.

We found knots of material within this outflow and were able to measure their speeds, said Dr. Ana K. Diaz-Rodriguez, also from the Astrophysical Institute of Andalucia.

The VLA observations gave important support to the idea that the older stars outflow had triggered the youngers stars formation process.

The scientists suggest that the jet from FIR 3 began to hit the clump of gas about 100,000 years ago, starting the process of collapse that eventually led to the formation of FIR 4.

Four other protostars in the region also could be the result of similar interactions, but the researchers found evidence for shocks only in the case of FIR 4.

While the evidence for this triggering scenario is strong, one fact appears to contradict it.

The younger star seems to be moving rapidly in a way that indicates it should have been formed elsewhere, apart from the region impacted by the older stars outflow.

This motion, however, might be an illusion possibly created by an outflow from the newer star itself, Dr. Osorio said.

We want to continue to observe it over a period of time to resolve this question.

The results were published in the May 3, 2017 issue of the Astrophysical Journal (arXiv.org preprint).

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Mayra Osorio et al. 2017. Star Formation Under the Outflow: The Discovery of a Non-thermal Jet from OMC-2 FIR 3 and Its Relationship to the Deeply Embedded FIR 4 Protostar. ApJ 840, 36; doi: 10.3847/1538-4357/aa6975

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Protostar May Have Triggered Formation of Another, Younger Star - Sci-News.com