Observing Early Galaxies and Their Secrets
Scientists have been exploring ancient galaxies, which gives us a remarkable look at how structures like our own Milky Way formed. This includes the Milky Way’s spiral shape, characterized by straight stars and gas bars at its center. However, these early galaxies are significantly larger and provide fresh insights into galactic formation.
One such galaxy, known as J0107A, existed 11.1 billion years ago, when the universe was only about a fifth of its current age. Researchers relied on data from the Atacama Large Millimeter/Sub-Millimeter Array (ALMA) in Chile and NASA’s James Webb Space Telescope for their findings.
What they discovered is quite fascinating: galaxies with stars and gases are over ten times bigger than the Milky Way and produce stars at rates around 300 times higher each year. However, J0107A is denser than our galaxy.
“These are massive galaxies, capable of forming stars at astonishing rates and with abundant gas, compared to those we see today,” noted Shuo Fan, an astronomer associated with a Japanese research institution, who is the lead author of the study published in the journal Nature.
Co-author Seido, an astronomer at Waka University in Japan, posed an intriguing question: “How did such a massive galaxy come to be in such an early universe?”
Interestingly, while there are galaxies today that form stars at comparable rates to J0107A, most are involved in mergers or collisions. J0107A, on the other hand, shows no signs of such processes.
J0107A and the Milky Way do share some characteristics.
“They both have impressive sizes and similar bar structures. Yet, the Milky Way had eons to develop its distinct shape, while J0107A did not,” Sato remarked.
Following the Big Bang, around 13.8 billion years ago, galaxies existed in chaotic conditions, far more prevalent than what we observe today. These conditions encouraged rapid bursts of star formation. While well-structured galaxies like the spiral Milky Way are common now, they weren’t like that 11.1 billion years ago.
“It’s surprising that J0107A resembles modern spiral galaxies, unlike other massive galaxies from earlier cosmic times, which often appear distorted,” Huang added.
“We may need to rethink our current theories on how galaxies are structured,” he continued.
The Webb telescope’s findings suggest that spiral galaxies emerged earlier than we previously thought, spanning great distances back to the universe’s infancy. J0107A is now recognized as one of the earliest examples of a barred spiral galaxy.
About two-thirds of the spiral galaxies we see today have bar structures, which likely function as stellar nurseries, drawing gas inward from the galaxy’s arms. This gas can condense into molecular clouds. Over time, gravity causes these clouds to collapse, forming regions that heat up and ultimately become new stars.
The bar in J0107A stretches roughly 50,000 light-years long, which amounts to a distance traveled in a year of 5.9 trillion miles (9.5 trillion km), according to Huang.
While Webb telescopes have been focusing on the formation of large early galaxies, their dynamics remain somewhat unclear, Saito noted.
