Star formation occurs in 'short bursts'

ESO's ALMA telescope has uncovered the growth of a protostar occuring in short bursts, revealing the process of stellar formation in greater clarity than ever before.

Published: November 5, 2015 at 12:00 pm

Distinct gaps in the jets of outflowing material from CARMA-7 can be seen in this image using ESO’s ALMA telescope. Each jet is nearly 1.5 trillion kilometres long. Credit: B. Saxton, NRAO/AUI/NSF; A Plunkett et al.; ALMA, NRAO/ESO/NAOJ


A study using ESO’s Atacama Large Millimeter/sub-millimeter Array (ALMA) has observed star formation within a cluster occurring in short, episodic bursts.

It is the first time such a pattern has been observed in a star cluster.

22 ‘episodes’ in all were recorded coming from protostar CARMA-7, which is located in Serpens South, a star cluster 1,400 lightyears from Earth.

As protostars are forming, they ingest the cosmic material that enables them to grow into stars. As this occurs, the stars eject surplus material they don’t need.

This is called ‘outflow’ and is important to astronomers for understanding the stellar formation process, as it is easier to detect than the incoming matter.

“Outflows are very common in astrophysics,” says co-author of the study Héctor Arce of Yale University.

“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.”

Fellow author Adele Plunkett is a Yale graduate student who works with ESO.

“This is the beginning of being able to understand cluster regions,” she says.

“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.”

The technology is enabling further study of the star formation process, including how often material is accreted or ejected over hundreds of years.

Further observations will enable the team to learn more about protostars in their most common environment.

“This result shows that when young stars grow they do so episodically, in little growth spurts, rather than steadily,” says co-author Pieter van Dokkum, Sol Goldman Professor of Astronomy and chair of Yale’s Department of Astronomy.


“They’ve learned to chew their food before they swallow.”


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