The James Webb Space Telescope (JWST) has discovered what may be the earliest star clusters in the universe.
The JWST discovered the five protoglobular star clusters – swarms of millions of stars held together by gravity – in the Cosmic Gems arc, a galaxy that was formed just 460 million years after the Big Bang.
The Cosmic Gems arc gets its name from its appearance: viewed from our solar system, the star-studded galaxy looks like a razor-thin crescent due to the strong gravitational pull of a foreground galaxy, which magnifies and distorts the appearance of the distant galaxy.
This galaxy is the most magnified region seen during the first 500 million years of our Universe, giving astronomers unprecedented insight into how the motions of the first stars shaped galaxies during the cosmic dawn.
The cosmic dawn covers the first billion years of the universe. About 400 million years after the Big Bang, the era of reionization began, in which the light of the emerging stars stripped the hydrogen of its electrons, resulting in a fundamental transformation of galaxy structures.
“The early universe is very different from what we expected,” says lead author of the study Angela Adamoan astronomer at Stockholm University, told Live Science. “Galaxies are more luminous, they form stars at breakneck speeds, and they do so in massive and dense star clusters. We are developing a new understanding of how early galaxies formed.”
The researchers published their results on June 24 in the journal Nature.
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Lights on at Cosmic Down
When stars are formed, they throw out material in the form of winds and jets of ionized plasma – a process known as stellar feedback.
“To form these five star clusters, this small galaxy had to operate at a very high efficiency,” said Adamo. “The stellar feedback from the stars into the star cluster must have been enormous.”
Scientists discovered the Cosmic Gems arc in 2018 using the Hubble Space Telescope. Usually, galaxies from such ancient times emit light that is far too faint to be detected by telescopes, but a phenomenon called gravitational lensing can help astronomers observe them.
As Einstein wrote in his general theory of relativityGravity is the curvature and distortion of space-time in the presence of matter and energy. This curved space, in turn, sets the rules for the movement of energy and matter.
This means that although light travels in a straight line, it can be bent and amplified by gravity. In this case, the galaxy SPT-CL J0615-5746 is located between the Cosmic Gems arc and our solar system, bending and amplifying the light from the early galaxy so that it can be observed with telescopes.
By pointing the JWST at this region of curved space, astronomers were able to observe the Cosmic Gems arc in unprecedented detail and resolve the five globular clusters embedded within it. They found that the clusters were incredibly dense, about three orders of magnitude denser than star-forming regions observed closer to Earth.
The clusters are among the first ever observed, but it is still unclear whether they are the first to exist at all, Adamo said.
“Basically, I would expect star formation to occur in clusters even in fairly primordial galaxies,” she added. “But to [massive] To grow into proto-globular clusters, the host galaxy must be able to create and retain enough mass in gas. So it all depends on how fast primordial galaxies can grow.”
To learn more about the cosmos’ first hotbeds in this region, the researchers will then conduct spectroscopic analysis with the JWST. This will allow astronomers to reconstruct the physical properties of the clusters, further constrain their age, and understand the influence of the clusters’ stars on their wider galaxy.