JWST helps discovery of ‘oldest galaxies and star clusters’
The James Webb Space Telescope has allowed Canadian researchers to identify the most distant globular clusters ever, that may contain the oldest known stars
A team of Canadian astronomers, including experts from the Dunlap Institute for Astronomy & Astrophysics in the University of Toronto‘s Faculty of Arts & Science, have used the James Webb Telescope (JWST) to identify the most distant globular clusters ever discovered – dense groups of millions of stars that may be relics containing the first and oldest stars in the universe.
Lamiya Mowla, a post-doctoral researcher at the Dunlap Institute for Astronomy & Astrophysics, and co-lead author of the study, which was carried out by the CAnadian NIRISS Unbiased Cluster Survey (CANUCS) team, said: “JWST was built to find the first stars and the first galaxies and to help us understand the origins of complexity in the universe, such as the chemical elements and the building blocks of life.
“This discovery in Webb’s First Deep Field is already providing a detailed look at the earliest phase of star formation, confirming the incredible power of JWST.”
the sparkler galaxy
In the finely detailed Webb’s First Deep Field image, the researchers zeroed in on what they’ve dubbed ‘the Sparkler galaxy’, which is nine billion light years away. This galaxy got its name for the compact objects appearing as small yellow-red dots surrounding it, referred to by the researchers as ‘sparkles’.
The team posited that these sparkles could either be young clusters actively forming stars – born three billion years after the Big Bang at the peak of star formation – or old globular clusters, which are ancient collections of stars from a galaxy’s infancy and contain clues about its earliest phases of formation and growth.
From their initial analysis of 12 of these compact objects, the researchers determined that five of them are not only globular clusters but among the oldest ones known.
Kartheik G Iyer, a post-doctoral researcher at the Dunlap Institute for Astronomy & Astrophysics and co-lead author of the study said: “Looking at the first images from JWST and discovering old globular clusters around distant galaxies was an incredible moment – one that wasn’t possible with previous Hubble Space Telescope imaging.
“Since we could observe the sparkles across a range of wavelengths, we could model them and better understand their physical properties – like how old they are and how many stars they contain.
“We hope the knowledge that globular clusters can be observed at from such great distances with JWST will spur further science and searches for similar objects.”
The Milky Way galaxy is known to have about 150 globular clusters, but how and when exactly these dense clumps of stars formed is not well understood. Astronomers know that globular clusters can be extremely old, but it is incredibly challenging to measure their ages. Using very distant globular clusters to age-date the first stars in distant galaxies has not been done before and is only possible with JWST.
Unique capabilities of JWST
Mowla said: “These newly identified clusters were formed close to the first time it was even possible to form stars.
“Because the Sparkler galaxy is much further away than our own Milky Way, it is easier to determine the ages of its globular clusters.
“We are observing the Sparkler as it was nine billion years ago, when the universe was only four-and-a-half billion years old, looking at something that happened a long time ago.
“Think of it as guessing a person’s age based on their appearance – it’s easy to tell the difference between a five- and a 10-year-old, but hard to tell the difference between a 50- and 55-year-old.”
CANUCS team lead Chris Willott from the National Research Council’s Herzberg Astronomy and Astrophysics Research Centre, added: “Our study of the Sparkler highlights the tremendous power in combining the unique capabilities of JWST with the natural magnification afforded by gravitational lensing.
“The team is excited about more discoveries to come when JWST turns its eye on the CANUCS galaxy clusters next month.”
JWST will observe the CANUCS fields starting in October 2022, leveraging its data to examine five massive clusters of galaxies, around which the researchers expect to find more such systems. Future studies will also model the galaxy cluster to understand the lensing effect and execute more robust analyses to explain the star formation histories.
The research is published in The Astrophysical Journal Letters.
Image: Thousands of galaxies flood this near-infrared, high-resolution image of galaxy cluster SMACS 0723. © NASA/ ESA/ CSA/ STScI.