The **James Webb Space Telescope** (JWST) has dramatically reshaped our understanding of the early Universe by discovering **massive galaxies** far earlier than previously theorized. Just weeks after commencing its observations, the JWST identified galaxies, including one dubbed **Y1**, that challenge existing models of galaxy formation, revealing a star formation rate (SFR) substantially higher than anticipated.
Researchers from the **Atacama Large Millimetre/submillimetre Array** (ALMA) have provided insights into this phenomenon through their study titled “A warm ultraluminous infrared galaxy just 600 million years after the Big Bang.” Published in the **Monthly Notices of the Royal Astronomical Society**, the research is led by **Tom Bakx**, a postdoctoral researcher at **Chalmers University of Technology** in Sweden.
Discovering Y1: A Star Factory
The Y1 galaxy is observed at **redshift 8.3**, meaning it existed approximately **600 million years** after the Big Bang. The light from Y1 has been traveling through space for over **13 billion years**. It has been characterized as a “superheated star factory,” with an SFR about **180 times greater** than that of the **Milky Way**, which forms roughly **1 solar mass** per year compared to Y1’s **180 solar masses** annually. This remarkable discovery suggests that early galaxies were significantly larger than current models account for.
According to Bakx, “We’re looking back to a time when the universe was making stars much faster than today.” The findings indicate that early galaxies like Y1 possessed more dust than expected, obscuring their high SFR and complicating our understanding of early galactic evolution.
The Role of Light and Dust
At the core of this discovery lies the properties of light. The JWST’s observations revealed red light emitted by heated dust within Y1, masking its prolific star formation. Bakx elaborated, “Previous observations revealed the presence of dust in this galaxy, making it the furthest away we’ve ever directly detected light from glowing dust.”
Young stars within massive gas clouds emit powerful light, some of which is undetectable to the human eye. This light illuminates surrounding dust, causing it to emit radiation in the radio spectrum, where ALMA excels. By focusing on **Band 9**, which corresponds to light at **0.44 mm wavelength**, ALMA has successfully measured the temperature of Y1’s dust.
The dust temperature in Y1 registers at approximately **90 Kelvin** (-180 Celsius or -292 Fahrenheit), considerably higher than the **20 to 40 Kelvin** range found in the Milky Way. This elevated temperature reflects Y1’s intense star formation activity. **Yoichi Tamura**, an astronomer at **Nagoya University**, remarked, “This confirmed that it really is an extreme star factory. Even though it’s the first time we’ve seen a galaxy like this, we think that there could be many more out there.”
The findings imply that galaxies like Y1 could have been commonplace in the early Universe. If rapid bursts of star formation were standard, they could elucidate the JWST’s unexpected discovery of massive galaxies from this epoch. Bakx stated, “We don’t know how common such phases might be in the early universe, so in the future, we want to look for more examples of star factories like this.”
Reevaluating Early Galactic Dust
Beyond addressing the size of early galaxies, the research reveals that these galaxies contain more dust than previously understood. Traditionally, astronomers believed that older stars, particularly evolved red giant stars, were the primary sources of galactic dust. The new insights suggest that warmer, less abundant dust can be just as luminous as larger quantities of cooler dust.
**Laura Sommovigo**, from the **Flatiron Institute and Columbia University**, noted, “Galaxies in the early universe seem to be too young for the amount of dust they contain.” She explained that the presence of hot, bright dust accounts for the findings without necessitating a large population of older stars.
The research concludes that Y1 serves as an extreme example of how dust-obscured star formation plays a critical role in the cosmic accumulation of stellar mass, with the true nature of these early galaxies only revealed through advanced observational techniques in the submillimetre regime.
The implications of these findings are profound, prompting a reevaluation of our understanding of galaxy formation and evolution in the early Universe. As astronomers continue to explore these distant galaxies, the boundaries of our cosmic knowledge are set to expand further.
