Astronomers using ALMA have imaged the episodic outflow of a young protostar known as CARMA-7. The twin jets -- each nearly 2.46 trillion kilometers long -- have distinct gaps, revealing that the star is growing by fits-and-starts. Credit: B. Saxton (NRAO/AUI/NSF); A. Plunkett et al.; ALMA (NRAO/ESO/NAOJ)
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered an adolescent protostar that is undergoing a rapid-fire succession of growth spurts. Evidence for this fitful youth is seen in a pair of intermittent jets streaming away from the star’s poles.
Known as CARMA-7, the protostar is one of dozens of
similar objects in the Serpens South star cluster, which is located
approximately 1,400 light-years from Earth. This clutch of nascent
stellar objects was first detected by and named for the Combined Array
for Research in Millimeter-wave Astronomy (CARMA) telescope.
"This
young protostar is undergoing periods of rapid growth separated by
periods of relative calm,” said Adele Plunkett, previously a National
Science Foundation (NSF) graduate research fellow at Yale University and
now a fellow at the European Southern Observatory (ESO) in Chile. "This
punctuated stellar formation provides important insights into the
chaotic interplay within this tightly packed cluster of young stars.”
All
stars form in dense clouds of dust and gas. As material condenses and a
star begins to evolve, surrounding material forms a flattened, rotating
disk that flows onto its surface. Because of the rotational energy of
the material in the disk and with the help of the star’s magnetic field,
a portion of that material gets ejected from the star’s poles, forming a
pair of jets that can be seen with radio telescopes like ALMA.
In
a recent survey of several protostars in the Serpens South region,
astronomers were surprised to find one with brilliantly defined jets
that seem to turn on-and-off with startling regularity, alternating from
one to the other in possibly as little as 100 years. The protostar and
its jets are oriented in such a way that the upper jet is mostly moving
away from us and the lower jet is mostly moving toward us.
These
prominent jets offer an otherwise hidden insight into the environment
of the accretion disk surrounding the protostar. Since the accretion
process is obscured by the surrounding dust and gas, the outflow is an
important observational proxy. However, since many stars are forming in
close proximity, astronomers needed powerful ALMA observations to
disentangle the chaotic outflow activity.
The ALMA data reveal
that there were 22 distinct ejection events associated with the CARMA-7
protostar. These outflows, which travel up to 2.46 trillion kilometers
from the protostar, also are impacting the surrounding cluster and
intermingling with other jets.
Previous observations were unable
to distinguish the outflow from CARMA-7 from the surrounding outflows
driven by neighboring protostars. “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,” said Plunkett. “This
shows how valuable ALMA is for observing a region like this.”
A paper describing these results is published in the journal Nature.
The
National Radio Astronomy Observatory is a facility of the National
Science Foundation, operated under cooperative agreement by Associated
Universities, Inc.
* * *
The Atacama Large
Millimeter/submillimeter Array (ALMA), an international astronomy
facility, is a partnership of the European Organisation for Astronomical
Research in the Southern Hemisphere (ESO), the U.S. National Science
Foundation (NSF) and the National Institutes of Natural Sciences (NINS)
of Japan in cooperation with the Republic of Chile. ALMA is funded by
ESO on behalf of its Member States, by NSF in cooperation with the
National Research Council of Canada (NRC) and the National Science
Council of Taiwan (NSC) and by NINS in cooperation with the Academia
Sinica (AS) in Taiwan and the Korea Astronomy and Space Science
Institute (KASI).
ALMA construction and operations are led by ESO
on behalf of its Member States; by the National Radio Astronomy
Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on
behalf of North America; and by the National Astronomical Observatory of
Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO)
provides the unified leadership and management of the construction,
commissioning and operation of ALMA.
Contact:
Charles Blue
(434) 296-0314
Email: cblue@nrao.edu
