JWST and ALMA Reveal Young Star Clusters and the Birth of the Universe's First Stars
16 January, 2025 / Read time: 5 minutes
Scientific PaperAstronomers have made groundbreaking discoveries about young star formation in the Large Magellanic Cloud (LMC) by utilizing the James Webb Space Telescope (JWST) alongside observations from the Atacama Large Millimeter/submillimeter Array (ALMA). The study, published in The Astrophysical Journal, provides new insights into the early stages of massive star formation beyond our galaxy.
About 6-7 billion years ago, super star clusters were the primary way stars formed, generating hundreds of new stars yearly. This form of star formation has been declining, with superstar clusters now rarely found in our Local Universe. Currently, only two super star clusters are known in the Milky Way, alongside one in the LMC, all of which are millions of years old. Recent observations from the JWST have provided evidence that the N79 region hosts a second super star cluster in the LMC, which is only 100,000 years old. This discovery allows astronomers to observe the birth of a super star cluster in our neighboring galaxy.
The LMC, a satellite galaxy of our own Milky Way, is located nearly 160,000 light-years from Earth. This relatively "nearby" distance makes it an ideal laboratory for studying extragalactic star formation. The JWST Mid-Infrared Instrument (MIRI) observed 97 young stellar objects (YSOs) in the N79 region of the LMC, where the newly discovered super star cluster, H72.97-69.39, is located. The abundance of heavy elements in the LMC is half as much as our Solar System's, with similar star-forming conditions to 6-7 billion years ago. This gives astronomers a glimpse of how star formation could have occurred in the universe's early days.
MIRI images show that the most massive YSOs gather near H72.97-69.39, and the less massive YSOs are distributed on the outskirts of N79—a process known as mass segregation. What was previously thought to be a single massive young star has now been revealed as clusters of five young stars, brought to light
ALMA has significantly contributed to studying YSOs in the LMC, particularly in the N79 region. Previous ALMA observations of this region revealed two colliding, parsec-long filaments of dust and gas. At their collision point lies super star cluster H72.97-69.39, home to the most luminous protostar identified by JWST. Filaments of molecular gas colliding could be the catalyst needed to create a super star cluster—and ALMA observations provide crucial context for understanding the larger-scale environment in which these YSOs are forming. This multi-wavelength research, combining data from JWST and ALMA, allowed astronomers to study the relationship between large-scale molecular cloud structures and the birth of protostars and clusters.
"Studying YSOs in the LMC gives astronomers a front-row seat to witness the birth of stars in a nearby galaxy. For the first time, we can observe individual low-mass protostars similar to the Sun forming in small clusters—outside of our own Milky Way Galaxy", shares Isha Nayak, lead author of this research, "We can see with unprecedented detail extragalactic star formation in an environment similar to how some of the first stars formed in the universe."
With this new research, scientists have observed YSOs at various evolutionary stages, from very young embedded protostars to more evolved objects ionizing their surroundings. This data provides insights into the complex chemistry occurring in these stellar nurseries, including the presence of ice, organic molecules, and dust, connecting the formation of stars to the broader story of how elements and compounds are distributed throughout the universe. These diverse observations deepen astronomers' understanding of the entire life cycle of massive stars. Nayak adds, "By shedding light on the birth of a super star cluster in a nearby galaxy, this research helps us understand the processes that shaped the first stellar clusters and galaxies in our universe and ultimately led to our existence."
Additional Information
The results of the observations are published in the following scientific paper:
Nayak et.al "JWST Mid-infrared Spectroscopy Resolves Gas, Dust, and Ice in Young Stellar Objects in the Large Magellanic Cloud" published in The Astrophysical Journal.
The original press release was published by the National Radio Astronomical Observatory (NRAO) of the United States, an ALMA partner on behalf of North America.
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organization 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 and Technology Council (NSTC) in Taiwan, 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.
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