Utilizing the James Webb Area Telescope (JWST), astronomers have found the secrets and techniques of early galaxies that pumped the toddler cosmos filled with mud, which might turn into important for the start of recent stars and the expansion of galaxies.
Nevertheless, whereas the JWST is highly effective sufficient to see many of those early galaxies, it’s nonetheless restricted with regards to delving into them in nice element. So, the crew on the coronary heart of this analysis labored round this by learning a a lot nearer and extra fashionable galaxy with many traits that resemble the universe’s first galaxies.
In lieu of having the ability to research the processes that occurred within the early universe that allowed galaxies to be seeded with “metals, (the time period astronomers use to explain components heavier than hydrogen and helium), the researchers turned their attention to a dwarf galaxy just 4.6 million light-years away.
“Directly studying the galaxies that populated the early universe is still very difficult, which is why observing a nearby galaxy like Sextans A, which presents similar chemical conditions, offers us a precious opportunity to understand how the first generations of stars evolved and what role they played in transforming the interstellar medium,” team leader Claudio Gavetti of the National Institute for Astrophysics (INAF) said in a statement.
How does Sextans A impersonate ancient galaxies?
The early universe was a pretty dull place in terms of chemistry. That is because it was dominated by the lightest element, hydrogen, with some helium and a tiny smattering of heavy elements, or metals. That means that the first generation of stars, so-called POP III stars, were correspondingly metal-poor.
During their lives, however, POP III stars fused hydrogen and helium in their cores to forge heavier elements. When these original stars reached the ends of their lives, they exploded in supernova explosions that dispersed these metals into the interstellar medium, the vast clouds of dust and gas between stars.
Eventually, dense and cool patches in these vast clouds collapsed under their own gravity, birthing the next generation of stars, POP II stars, which, thanks to the supernova deaths of their predecessors, were richer in metals.
Our own star, the sun, is classed as a POP I star, meaning it is even richer in metals than these second-generation stars. However, not all modern galaxies are so metal-rich; this is especially true for dwarf galaxies like Sextans A, even though it lies at the outer edge of our cosmic backyard, known as the “local group.”
Sextans A is so metal-poor that it is estimated to contain only between 1% and 7% of the heavy elements found in the sun. That makes it a great proxy for the study of metal-poor early galaxies.
Using the JWST’s NIRCam (Near-InfraRed Camera) and MIRI (Mid-Infrared Instrument) instruments, Gavetti and colleagues obtained high-resolution observations of Sextans A that allowed them to map the dwarf galaxy’s entire population of stars during an evolutionary phase known as the “asymptotic red giant branch.”
This phase occurs when stars larger than the sun exhaust helium in their cores, creating an inert carbon heart, but nuclear fusion continues in outer alternating helium- and hydrogen-burning layers. These stars “puff out” as a result of this and can undergo thousandfold increases in brightness.
The team’s findings revealed that around 90% of the asymptotic red giant branch stars they studied were not surrounded by envelopes of dust. However, around 20 or so of these stars were embedded in thick dust shells. They also found that these “dust factories” formed between 2 billion and 3 billion years ago from stars with an initial mass about 1.5 times the mass of the sun.
This research is a leap forward in understanding which stars in the early universe were most likely to create the metal dust that would have enriched the next generations of stars. That means it helps paint a complete picture of how the universe as we see it today took shape.
The scientists behind this study say that this type of research would have been impossible before the launch of Webb.
“The JWST allows us to observe in unprecedented detail environments that until a few years ago were beyond our reach,” team member Flavia Dell’Agli of the INAF. “The value of these data lies not only in the images, but in the ability to compare them with theoretical models and verify how correctly they describe the evolution of stars.”
The team’s research was published on Monday (July 20) in The Astrophysical Journal.
