The history of how stars and galaxies came to be and evolved into the present day remains among the most challenging astrophysical questions to solve yet, but new research brings us closer to understanding it.
A new study by an international team lead by Dr. Angela Adamo at Stockholm University has uncovered new information about young galaxies during the Epoch of Reionization. The James Webb Space Telescope (JWST) observed the galaxy Cosmic Gems arc (SPT0615-JD) and determined that the galaxy’s light was released 460 million years after the big bang.
This galaxy is unique because it is amplified by a phenomenon known as gravitational lensing, which has not been found in other galaxies created during that time period. The Cosmic Gems arc’s magnification enabled the team to explore tiny structures within a baby galaxy for the first time. The authors discovered that the Cosmic Gems arc has five young large Star clusters are where stars form. “The surprise and astonishment was incredible when we opened the JWST images for the first time” according to Adamo.
The mystery of the early Universe
The Epoch of Reionization (EoR) is a critical period in the evolution of the universe, occurring during the first billion years after the Big Bang. During this time, the Universe underwent a significant shift. Initially, it was filled with neutral hydrogen gas, but this altered throughout the EoR. The Universe’s matter transitioned from neutral to totally ionized, with atoms losing their electrons. This change is thought to have been driven by the Universe’s early galaxies.
To study the earliest galaxies, we need to observe objects at far distances in space. However, observing small details at large distances is challenging. Gravitational lensing, a method where a celestial body’s strong gravity distorted light, allows astronomers to observe finer details in distant galaxies, similar to the magnifying glass effect.
Star formation is a process in which galaxies build their stellar population, with a significant fraction of stars forming in star clusters, which can vary in size and age, and the origin of globular clusters remains a mystery.
New discoveries on the genesis of the earliest stars and galaxies
In a new study published in the scientific journal Nature, scientists report the finding of star clusters in a galaxy whose light traveled through a gravitational lens on its route to Earth. “This achievement could only be possible thanks to JWST unmatched capabilities,” says Dr. Adélaïde Claeyssens of Stockholm University, co-author of the publication. The galaxy SPT0615-JD, commonly known as the Cosmic Gems Arc, is found in the distant Universe. The light that we see now came from this galaxy only 460 million years after the Big Bang. Astronomers analyze this object to view back 97% of cosmic time.
The team used the Near Infrared Camera (NIRCam) onboard the JWST to study the Cosmic Gems Arc, revealing a chain of bright dots mirrored from one side to the other, which were found to be five young massive star clusters.
The Cosmic Gems arc observations reveal gravitationally bound stellar clusters with a three-times larger density than typical young star clusters in the Universe. These clusters were formed recently within 50 million years and are massive, smaller than globular clusters. The observations provide insight into the works of infant galaxies and the formation of globular clusters.
Look forward
Researchers are studying star clusters in young galaxies born shortly after the Big Bang to better understand how and where globular clusters form. Young galaxies are believed to drive reionization during the Early Universe Reionization (EoR). The team plans to build a larger sample of similar galaxies and conduct spectroscopic observations of the Cosmic Gems Arc galaxy to map star formation rate and ionizing photon production efficiency.
Reference – Star clusters observed within a galaxy in the early Universe