ALMA Views the Episodic Outflow of Protostar CARMA-7

Enlarge * Astronomers using the Atacama Large Millimeter/sub-millimeter Array (ALMA) have imaged the episodic outflow of a young protostar known as CARMA-7. The twin jets — each nearly 1.5 trillion kilometers long — have distinct gaps, revealing that the star is growing by fits and starts. (Image courtesy of B. Saxton, NRAO/AUI/NSF; A Plunkett et al.; ALMA, NRAO/ESO/NAOJ)

A new study led by Yale University reveals a cluster of young stars that develop in distinct, episodic spurts.

It is the first time astronomers have seen such a growth pattern within a star cluster — a chaotic, turbulent environment that is common for star formation. Previous observations have focused on stars forming in more isolated regions of space.

In a study published this week in the journal Nature, astronomers described the cosmic convulsions within Serpens South, a star cluster 1,400 light years from Earth. The researchers focused in particular on a protostar called CARMA-7.

The researchers recorded 22 “episodes” in which CARMA-7 experienced the gravitational push-pull that characterizes star formation. As protostars ingest raw material, they have counter-balancing emissions of material they don’t need. Such “outflow” is important to researchers because it can be measured more easily, unlike the hard-to-detect incoming matter.

“Outflows are very common in astrophysics,” said co-author Héctor Arce, an astronomy professor at Yale whose research group focuses on outflow dynamics. “They are good indicators of protostars, evolved stars, and even supermassive black holes. They tell us that there is a central, massive object in the outflow origin, with a surrounding accretion disc.”

The first author of the paper is Adele Plunkett, a recent Yale graduate student now working with the European Southern Observatory (ESO) in Santiago, Chile. Plunkett and her colleagues used data from the Atacama Large Millimeter/sub-millimeter Array (ALMA) in Chile to conduct the research.

“This is the beginning of being able to understand cluster regions,” Plunkett said. “In the past, we only saw cumulative outflows. To be able to observe individual outflows, with distinct ejection events, was exciting — and something we could only do with ALMA.”

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