Armagh Observatory and Planetarium, together with former PhD student Venu Kalari and a team of international researchers, have identified young, pre-main sequence stars in the low-metallicity dwarf galaxy WLM, using the James Webb Space Telescope (JWST).
On Christmas Day 2021, NASA and ESA launched the James Webb Space Telescope (JWST), a cutting-edge successor to the Hubble Space Telescope. Unlike Hubble, which primarily observes visible light, JWST is designed to study the universe in infrared, allowing astronomers to peer through cosmic dust and detect celestial objects that would otherwise remain hidden.
In a groundbreaking study, astronomers discovered twelve young, metal-poor pre-main sequence stars in the distant dwarf galaxy Wolf–Lundmark–Melotte (WLM), located 3 million light-years away. These stars, estimated to be less than 10 million years old, were detected through their infrared signatures at JWST wavelengths of 2.5 and 4.3 microns.
WLM is one of the most metal-poor galaxies in our local universe, with a present-day metal fraction just 10% that of our solar system. The discovery of circumstellar disks around these young stars provides valuable insights into how stars formed in the early universe, during the period known as the cosmic noon, when star formation was at its peak billions of years ago.
Lead researcher Venu Kalari expressed the significance of the findings: “For the first time, we have been able to detect young stars with surrounding gas and dust in a distant, low-metallicity environment. This provides a unique glimpse into star formation under conditions similar to those of the early universe.”
This discovery challenges prior assumptions about star formation in metal-poor environments. Traditionally, detecting circumstellar disks in such galaxies was thought to be difficult, as metals – key components of dust – are scarce. Yet, the ability to spot young forming stars in WLM, nearly 16 times further away than previous studies, has opened new avenues for future JWST observations.
Dr. Kalari added: “We were expecting to find fully formed massive stars, but instead, we identified young protostars surrounded by dust and gas, an unexpected and exciting result.”
The stars were found within a compact stellar cluster approximately 30 light-years across, located in the HII region [HM95]-9. These are the most distant and metal-poor pre-main sequence stars ever identified, offering a rare opportunity to study how star formation in metal-poor galaxies compares to the conditions in our own Milky Way.
This research suggests that star formation in metal-poor galaxies may follow similar processes to those in the Milky Way, despite previous expectations of significant differences due to lower metal content. The study paves the way for future JWST observations to investigate such stars in even greater detail, helping astronomers better understand the evolution of galaxies and star formation over cosmic time.
The discovery also underscores JWST’s unparalleled capabilities in unveiling hidden aspects of the universe, allowing scientists to study celestial objects at an unprecedented distance and level of detail.
This discovery is a huge leap in our ability to observe young forming stars in distant galaxies. Until now, the furthest young forming stars were detected in the Small Magellanic Cloud, approximately 200,000 light-years away. The detection of young stars in WLM – 16 times further away – represents an incredible technological achievement.
Prof. Vink from Armagh Observatory & Planetarium concludes: “The ability to detect forming stars at such a vast distance demonstrates the power of JWST and marks an exciting step forward in our understanding of the early universe.”
For more details on this discovery and future research, visit Armagh Observatory and Planetarium’s website.
The whole WLM galaxy taken by the Blanco 4.1m telescope is shown. The cluster shown by the white circle, is where the young stars were identified. It is zoomed-in a JWST image at three wavelengths, 90, 150, and 430 microns shown in blue, green, and red respectively. Young, forming stars are located around the faint nebulous structure visible in red. The images demonstrate the potential to identify and characterize individual stars forming in very distant galaxies. Image credit: Whole WLM galaxy: NOIRLab/NSF/AURA/CTIO/Local Group Survey Team and T.A. Rector (University of Alaska Anchorage) JWST image: NASA, ESA, CSA, Venu Kalari