The James Webb Space Telescope (JWST) has dramatically altered our understanding of the early universe by revealing massive galaxies that challenge existing astronomical theories. Just weeks after initiating observations, the telescope identified galaxies that are considerably more massive than previously anticipated. This unexpected discovery has prompted researchers to seek explanations, leading to new findings published in the Monthly Notices of the Royal Astronomical Society.
The lead researcher, Tom Bakx, a postdoctoral researcher at Chalmers University of Technology in Sweden, has focused on a galaxy labeled Y1. At a redshift of 8.3, this galaxy is observed as it existed approximately 600 million years after the Big Bang. The light from Y1 has traveled over 13 billion years to reach us, providing a unique glimpse into the universe’s infancy.
Researchers have dubbed Y1 a “superheated star factory” due to its extraordinarily high star formation rate (SFR). Y1’s SFR is about 180 times that of the Milky Way, producing approximately 180 solar masses of stars annually, compared to the Milky Way’s 1 solar mass per year. This finding may help explain the unexpectedly large sizes of early galaxies, as current theories do not accommodate such extensive star formation.
The analysis of Y1’s light reveals red wavelengths emitted from superheated dust, which conceals the galaxy’s high SFR. Bakx commented, “We’re looking back to a time when the universe was making stars much faster than today.” He highlighted that Y1 is the furthest galaxy from which astronomers have directly detected light from glowing dust, suggesting its unique characteristics.
Understanding star formation involves examining complexes of massive gas clouds, where young stars emit brilliant light. This light illuminates surrounding gas and dust, which emits radiation in the radio spectrum, a domain where the Atacama Large Millimetre/submillimetre Array (ALMA) excels. Observing at a wavelength of 0.44 mm, ALMA determined Y1’s temperature, revealing that its dust is around 90 Kelvin (approximately -180 degrees Celsius or -292 degrees Fahrenheit). For context, the Milky Way’s dust temperature ranges from 20 to 40 Kelvin.
Co-researcher Yoichi Tamura, an astronomer at Nagoya University in Japan, noted, “The temperature is certainly chilly compared to household dust on Earth, but it’s much warmer than any other comparable galaxy we’ve seen.” This elevated temperature supports Y1’s classification as an extreme star factory, with potential implications that such galaxies may have been commonplace in the early universe.
The findings also suggest that rapid bursts of star formation might explain why the JWST has uncovered massive galaxies so early in cosmic history. Bakx expressed the interest in searching for more examples of such star factories, emphasizing the need for further exploration with ALMA’s high-resolution capabilities.
Additionally, the research indicates that early galaxies may contain more dust than previously thought possible. Traditionally, it was believed that older stars, particularly evolved red giant stars, were the main sources of galactic dust. However, if the dust is warmer, it can emit as much light as larger quantities of cooler dust. Bakx and his colleagues argue that this warmer dust can account for the observations of dust in early galaxies, despite their relative youth.
Co-author Laura Sommovigo from the Flatiron Institute and Columbia University remarked, “Galaxies in the early universe seem to be too young for the amount of dust they contain.” She elaborated that a small quantity of warm dust can produce brightness comparable to larger masses of cooler dust, which has been observed in Y1.
The research concludes that this extreme example of dust-obscured star formation plays a significant role in the cosmic buildup of stellar mass, a phenomenon that can only be fully appreciated through comprehensive observations in the submillimetre regime. As the JWST continues its exploration, it promises to unlock further mysteries of the universe’s early epochs.
