ALMA telescope spots protostar hitting growth spurts

The jets of CARMA-7 have been turning on and off, on and off, sometimes within the span of just 100 years.

By Brooks Hays
ALMA telescope spots protostar hitting growth spurts
The twin jets of adolescent protostar CARMA-7 reveals a series of stop-and-start growth spurts. Photo by ALMA/ESO

NEW HAVEN, Conn., Nov. 4 (UPI) -- The growing pains of an adolescent star have been captured on film.

As detailed in a new paper, published in the journal Nature, the protostar CARMA-7 has been experiencing a series of sudden growth spurts.


Two gas jets streaming from the protostar's poles reveal the fits and starts of the spasmodic teen's maturation. The jets were recently imaged by the Atacama Large Millimeter/submillimeter Array (ALMA) and analyzed by a team of astronomers at Yale University.

"This young protostar is undergoing periods of rapid growth separated by periods of relative calm," explained lead study author Adele Plunkett, formerly a research fellow at Yale and now a fellow at the European Southern Observatory in Chile. "This punctuated stellar formation provides important insights into the chaotic interplay within this tightly packed cluster of young stars."

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Most young stars form an accretion disk as more and more gas and dust is pulled into the growing stellar orb. The motion of the flattened, spinning disk causes some of its material to be expelled, appearing as jets.

Analysis by Plunkett and her colleagues suggests the jets of CARMA-7 have been turning on and off, on and off, sometimes within the span of just 100 years.


Because accretion discs obscure the more intimate details of a young star's evolution, the out-flowing jets often offer the best clues as to what's going on.

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"They are good indicators of protostars, evolved stars, and even supermassive black holes," co-author Hector Arce, an astronomy professor at Yale, said of outflows. "They tell us that there is a central, massive object in the outflow origin, with a surrounding accretion disc."

But young stars often form in close proximity, each disk and their jets forming a confusing haze of stellar material. ALMA can help scientists sort through the mess and secure clear images of these jets. Previous attempts to image CARMA-7 were unsuccessful at finding the sporadic outflows amid the chaos.

"These sources are so young and embedded and neither optical nor near-infrared light could give a complete picture of the protostar and its outflow," Plunkett said of earlier imaging work. "This shows how valuable ALMA is for observing a region like this."

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"This is the beginning of being able to understand cluster regions," Plunkett added. "In the past, we only saw cumulative outflows. To be able to observe individual outflows, with distinct ejection events, was exciting."

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