Some of the first stars seen so far are coming to light in one of the first images from the James Webb Space Telescope.
Formed about 800 million years after the Big Bang, stars live in dense groups called globular clusters and surround a distant galaxy called Sparkler, astronomers report on October 1 Astrophysical journal letters. Globular clusters are often home to some of the oldest stars in contemporary galaxies like our own, but it’s hard to know their exact age. The new finding could help researchers pinpoint when such clusters began to form.
Compared to a galaxy, globular clusters are tiny, making them difficult to see from across the universe. But this time, a giant natural lens in space helped. The flare is one of thousands of galaxies that lie far behind a massive and much closer cluster of galaxies called SMACS 0723which was the subject of the first publicly released science image from the James Webb Space Telescope, or JWST (Serial number: 7/11/22). The cluster distorts space-time in such a way that the light from more distant galaxies behind it is magnified.
For all those remote galaxies, that extra magnification brings out details that have never been seen before. An elongated galaxy surrounded by yellowish spots caught the attention of astronomer Lamiya Mowla and her colleagues.
“When we first saw it, we noticed all these little dots around it that we call ‘the flashes,'” says Mowla of the University of Toronto. The team I wondered if the flashes could be globular clustersclose-knit families of stars believed to have been born together and remain together throughout their lives (Serial number: 10/15/20).
“The pending question that still remains is how were globular clusters 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 in “cosmic dawn”, when the stars were able to form for the first time (Serial number: 4/3/22)?
Light from Bengal takes about 9 billion years to reach Earth, so if the flares are globular clusters that shone so long ago, they could help astronomers answer that question.
Mowla and his colleagues used JWST data to analyze the wavelengths of the light coming from the flashes. Some of them appear to be forming stars at the time their light left the clusters. But some had formed all their stars 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.
That means the oldest stars in the flashes could have formed about 13 billion years ago. Since the universe is 13.8 billion years old, “there’s only a short period of time after the Big Bang when these could have formed,” she says.
In other words, these cumulus clouds were born at sunrise, not at noon.
Studying more globular clusters around ancient galaxies could help determine whether such clusters are common or rare early in the universe’s history. They could also help unravel the formation histories of galaxies, say Mowla and Iyer. His team has proposed that observations be made in the first year of JWST that could do just that.
Being able to identify tiny structures like globular clusters from so far away was nearly impossible before JWST, says astronomer Adélaïde Claeyssens of Stockholm University. She was not involved in the new work, but led a similar study earlier this year. of multiple galaxies magnified by the cluster SMACS 0723.
“This is the first time that we have shown that, with James Webb, we will observe many of these galaxies with really tiny structures,” says Claeyssens. “James Webb will be a game changer on this field.”