The James Webb Deep Field image has revealed a nine billion-year-old galaxy home to some of the oldest known star clusters.
Canadian researchers have discovered the most distant globular clusters ever discovered using the James Webb Space Telescope (JWST). The first and oldest stars in the universe may reside in these dense groups of millions of stars. This week, The Astrophysical Journal Letters published the analysis of Webb’s First Deep Field image showing some of the universe’s earliest galaxies. According to Lamiya Mowla, Dunlap Fellow at the Dunlap Institute for Astronomy & Astrophysics at the University of Toronto and co-lead author of the study, the JWST was built to discover the first stars and galaxies in the universe and to help us understand the origins of complexity in the universe.
JWST’s remarkable power is already being demonstrated in Webb’s First Deep Field by revealing the earliest phases of star formation. This finely detailed Webb Deep Field image focuses on an object nine billion light years away called “the Sparkler galaxy.” According to the researchers, the galaxy got its name from small yellow-red dots surrounding it that appear as sparks. These sparks could either be young star clusters—born three billion years after the Big Bang, when star formation was at its peak—or old globular clusters.
During the early phases of galaxy formation, globular clusters provide clues as to what a galaxy’s earliest phases were like. The researchers found that five of the compact objects are not only globular clusters, but some of the oldest as well. Seeing the first JWST images and discovering old globular clusters around distant galaxies was a wonderful experience that Hubble had not been able to show, revealed Kartheik G. Iyer, a Dunlap Fellow at the Dunlap Institute for Astronomy & Astrophysics at the University of Toronto.
Due to the fact that scientists could observe the sparkles at different wavelengths, they were able to model them better and determine their physical properties, such as their age and the number of stars. Observing globular clusters at such great distances with JWST may lead to further research and searches for similar objects. Around 150 globular clusters are known to exist in our Milky Way galaxy, but how and when they formed is unclear. It is incredibly challenging to measure the ages of globular clusters, despite the fact that they are known to be extremely old. JWST is the only telescope capable of age-dating the first stars in distant galaxies using distant globular clusters.
According to Mowla, these clusters formed as close as possible to the first time stars could form. In the Sparkler galaxy, globular clusters can be determined more easily because they are much farther away than our own Milky Way galaxy. According to Mowla, the James Webb image of the Sparkler Galaxy is showing us essentially what the galaxy was like some nine billion years ago when the universe is thought to have been only four-and-a-half billion years old. “Think of it as guessing a person’s age based on their appearance—it’s easy to tell the difference between a 5- and 10-year-old, but hard to tell the difference between a 50- and 55-year-old,” Mowla explained.
Until now, the Hubble Space Telescope (HST) has not been able to observe the compact objects surrounding the Sparkler galaxy. JWST’s increased resolution and sensitivity enabled Webb’s First Deep Field image to show the tiny dots surrounding the galaxy for the first time. A gravitational lensing effect magnifies the Sparkler galaxy by a factor of 100 because of the SMACS 0723 galaxy cluster in the foreground that distorts what is behind it. In addition, three separate images of the Sparkler galaxy are available to scientists due to gravitational lensing.
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