In one of the first images taken by the James Webb Space Telescope, some of the earliest known stars are being revealed.
The stars were created around 800 million year after the Big Bang. They are composed of dense groups called “globular clusters” and their surrounds The Sparkler is a distant galaxy. astronomers report in the Oct. 1 Astrophysical Journal Letters. Globular clusters often host some of the oldest stars in contemporary galaxies such as our own, but it’s hard to tell their exact age. Researchers may be able to pinpoint the time when these clusters formed.
Gglobular clusters are smaller than a galaxie, making them difficult to spot from anywhere in the universe. This time, however, the natural space lens was a huge help. The Sparkler is just one of the thousands of galaxies far behind. SMACS 0723 is a massive cluster of galaxies that is much closer than the rest.This was the subject of the JWST’s first ever publicly available science image.SN: 7/11/22). The cluster distorts the spacetime so that light from other galaxies is magnified.
The extra magnification of distant galaxies brings out details that were never seen before. Lamiya Mowla, an astronomer, and her colleagues noticed a long-circumscribed galaxy that was surrounded by yellowish blobs.
“When we first saw it, we noticed all those little dots around it that we called ‘the sparkles,’” says Mowla, of the University of Toronto. The team Have you ever wondered if the sparkles could be globular clusters of light?Close-knit stars from close-knit families that were thought to be born together and remain close to each other their entire lives.SN: 10/15/20).
“The outstanding question that there still is, is how were the globular clusters themselves born?” Mowla says. Were they born at “cosmic noon,” 10 billion years ago, when star formation throughout the universe peaked? Or did they form 13 billion years ago at “The dawn of the cosmic universe,” when stars were first able to form at all (SN: 3/4/22)?
The light from the Sparkler takes 9 billion years for it to reach Earth.
Mowla used JWST data for her analysis of the wavelengths coming from the sparkles. Some of them seem to have formed stars when their light left the clusters. Some stars had already formed long before.
“When we see them, the stars are already about 4 billion years old,” says astrophysicist Kartheik Iyer, also of the University of Toronto.
This means that the oldest stars visible in the sparkles could have formed around 13 billion years ago. Since the universe is 13.8 billion years old, “there’s only a short amount of time after the Big Bang when these could have formed,” he says.
These clusters were therefore born at dawn and not at noon.
Studying more globular clusters around ancient galaxies could help determine if such clusters are common or rare early on in the universe’s history. They could also help unravel galaxies’ formation histories, say Mowla and Iyer. Their team has proposed observations to be made in JWST’s first year that could do just that.
Being able to pick out tiny structures like globular clusters from so far away was almost impossible before JWST, says astronomer Adélaïde Claeyssens of Stockholm University. Although she was not part of the new research, she led an earlier similar study. Multi-galaxies magnified by SMACS 0723 cluster.
“It’s the first time we showed that, with James Webb, we will observe a lot of these type of galaxies with really tiny structures,” Claeyssens says. “James Webb will be a game changer for this field.”
