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Astronomers have made new discoveries about young star formation in the Large Magellanic Cloud (LMC), using the James Webb Space Telescope (JWST), along with observations from the Atacama Large Millimeter/submillimeter Array (ALMA). The study, in The Astrophysical Journal, gives new insight into the early stages of massive star formation outside our galaxy.

Six- to seven-billion years ago, super star clusters were the main way stars were formed, producing hundreds of new stars every year. This type of star formation has been on the decline, with super star clusters found very rarely in our local universe. Only two super star clusters are now known in the Milky Way, and one in the LMC, all of which are millions of years old.

JWST observations have now provided unambiguous proof that the N79 region is host to a second super star cluster in the LMC, aged a mere 100,000 years old. This discovery now allows astronomers to witness 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, and its face-on orientation to Earth, make 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, similar star-forming conditions to 6–7 billion years ago. This gives astronomers a glimpse at how star formation could have taken place in the early days of the universe.

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 by JWST's precise imaging. One of the five young stars is more than 500,000 times more luminous than the sun, with more than 1,550 young stars surrounding it, as revealed by JWST Near InfraRed Camera (NIRCam.)

ALMA has made significant contributions to the study of 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 now 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 enhance the understanding astronomers previously had about the full 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 own existence."