by Using the James Webb Space Telescope (JWST), astronomers discovered star clusters in the “Cosmic Gems” arc that existed just 460 million years after the Big Bang. This is the first discovery of star clusters in an infant galaxy, as it was when the universe was 13.8 billion years old less than 500 million years old.
The Cosmic GEMS arc is a gravitationally lensed infant galaxy, first discovered by the Hubble Space Telescope and officially named SPT0615-JD1, about 13.3 billion light-years from Earth. That means that light from this galaxy, seen by the JWST, has been traveling to Earth for about 97% of the universe’s lifetime.
The international team of astronomers behind this discovery discovered five massive young star clusters in the Cosmic Gems arc. These clusters existed during a period when young galaxies were undergoing an intense burst of star formation and emitting huge amounts of ultraviolet light. This radiation may be responsible for triggering one of two major phases in the evolution of the universe: the era of cosmic reionization.
Studying these five star clusters could teach astronomers a great deal about this early period in the cosmos.
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“The surprise and amazement was incredible when we opened the JWST images for the first time,” Angela Adamo of Stockholm University and the Oskar Klein Center in Sweden, and team leader, said in a statement. “We saw a small chain of bright dots mirrored from one end to the other – these cosmic gems are star clusters! Without JWST, we wouldn’t have known we were looking at star clusters in such a young galaxy! “
The newly discovered star clusters in the Cosmic Gems arc are remarkable for their massive and compact nature. The density of five star clusters is much higher than that of nearby star clusters.
A helping hand from Einstein
The era of reionization is so important because it was the stage at which the first light sources in the cosmos — the early galaxies, stars, and supermassive black hole-powered quasars — provided the energy to split electrons away from neutral hydrogen. fill the universe. .
The newly discovered star clusters are located in a very small region of their galaxy but are responsible for most of the ultraviolet light coming from that galaxy, meaning that reionization may have been primarily driven by clusters like these.
By studying reionization, scientists can learn more about the processes that formed large-scale structures in the universe. This can show how a very fine distribution of matter during the early cosmic time gave rise to the highly structured universe of galaxies (and galaxy clusters) that astronomers see in the later universe.
Specifically, these five early star clusters can show where stars formed and how they were distributed during the cosmos’ infancy. This provides a unique opportunity to study star formation as well as the workings within infant galaxies at an unprecedented distance, the study team says.
“JWST’s incredible sensitivity and angular resolution at near-infrared wavelengths, combined with gravitational lensing provided by the foreground galaxy cluster, made this discovery possible,” said Larry Bradley, principal investigator of the observing program that captured these data, in the statement . . msgstr “No other telescope could have made this discovery.”
To see such distant objects as they were in the early universe, the JWST uses a principle from Einstein’s 1915 theory of gravity: general relativity.
General relativity suggests that objects of mass cause the fabric of space and time, united as a four-dimensional entity called “space-time,” dense. The more mass an object has, the more space-time collapses as a result.
When light from background sources passes this warping, its path becomes curved. The closer the light gets to the warping object, the more its path curves. As a result, light from one object can reach an observer, like the JWST, more than once and at different times.
This means that light sources can appear in multiple places in the same image, shift their positions to apparent positions, or, more usefully, increase their light. The latter phenomenon is called “gravitational lensing”, and the body between a distant background object and the Earth is called a “lensing object”.
In this case, the lensing object is a lensing galaxy cluster called SPT-CL J0615−5746, and the background objects are the Cosmic Gems, their star clusters, and two distant lensing galaxies.
“What’s special about the Cosmic Gems arc is that we can resolve the galaxy to parsec scales thanks to gravitational lensing!” Adamo said.
How do globular clusters come together?
One promising follow-up study that came out of this JWST observation of early star clusters concerns how star arrangements, known as “globular clusters,” are formed. As seen in our galaxy, the Milky Way, globular clusters are ancient remnants of an intense burst of star formation in the early universe.
Scientists aren’t entirely sure how these globular conglomerates of gravitationally tightly packed stars come together, but it could be crucial that massive and compact clusters of young stars in the Cosmic Gems arc are the early stages of formation. global cluster. This means they could provide an extremely useful window into the early stages of globular cluster birth.
These five star clusters may also help to understand other aspects of cosmic evolution.
“The high stellar densities found in the clusters give us the first indication of the processes taking place inside them, giving new insights into the possible formation of supermassive stars and black hole seeds, which are important for galaxy evolution,” Adamo. said.
The study of the Cosmic Gems arc will continue and the team behind this research is already planning to observe this early galaxy with JWST’s Near-Infrared Spectrograph (NIRSpec) and Mid-Infrared Instruments (MIRI) instruments during Cycle 3 of the $10 billion space telescope’s operations. .
“The NIRSpec observations will allow us to confirm the redshift of the galaxy and study the ultraviolet emission of the star clusters, which will be used to study their physical properties in more detail,” said Bradley. “MIRI observations will allow us to study the properties of ionized gas.”
These spectroscopic observations should reveal how intense star formation was in the active sites of this infant galaxy.
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The astronomers behind this study now intend to study other galaxies to hunt for star clusters like these five.
“I am sure that other systems like this are waiting to be revealed in the early universe, which will enable us to increase our understanding of the early galaxies,” said team member Eros Vanzella from the National Institute of Astrophysics (INAF).
The team’s research was published on Monday (June 24) in the journal Nature.
