Is it possible for stars to have formed in the early universe?

The fundamental question of astronomy, ‘How did the first stars and galaxies form?’ is being investigated with the help of NASA’s James Webb Space Telescope. The JWST Advanced Deep Extragalactic Survey, or JADES, has devoted 32 days of telescope time to uncover and characterize distant galaxies. Already, JADES has discovered hundreds of galaxies that existed when the universe was less than 600 million years old, and has identified galaxies with a multitude of young, hot stars. The data being collected by JADES is providing new insights into the formation of stars and galaxies, helping astronomers better understand our place in the universe.

The JADES program, which is co-led by Marcia Rieke of the University of Arizona in Tucson, aims to answer many important questions about the formation of galaxies. These include how the earliest galaxies formed, how quickly they formed stars, and why some galaxies terminate star formation. JADES seeks to further our knowledge and understanding of galaxy formation, which can be used to explain the universe as we know it today. The program will likely provide insight into the evolution of galaxies over time and could potentially shed light on the origin and destiny of our universe.

Ryan Endsley of the University of Texas at Austin recently led an investigation into galaxies that existed during the crucial epoch of reionization, 500 to 850 million years after the Big Bang. This epoch marked a transition in the universe from being filled with a gaseous fog that made it opaque to energetic light, to becoming transparent. Scientists debate whether active, supermassive black holes or galaxies full of hot, young stars were the primary cause of reionization. Through his investigation, Endsley hopes to shed light on this cosmic transition period and its effects on our universe.

The JADES program, led by Dr. Endsley, has used Webb’s NIRSpec (Near-Infrared Spectrograph) instrument to study galaxies and look for signatures of star formation. The results have been surprising, as almost every single galaxy studied shows strong emission line signatures indicating intense recent star formation. Dr. Endsley notes that the early galaxies were very effective at creating hot, massive stars, which is evidenced by the abundance of star formation found in the galaxies observed.

These bright, massive stars emitted torrents of ultraviolet light, which transformed the opaque gas to transparent by ionizing the atoms and removing electrons from their nuclei. It is thought that these early galaxies, with their large population of hot, massive stars, were the main drivers of the reionization process, which later resulted in the distinctively strong emission lines from the reuniting of electrons and nuclei. Endsley and his colleagues also discovered that these young galaxies had periods of rapid star formation followed by quieter times with fewer stars forming. This pattern may have been due to galaxies capturing clumps of gaseous material needed for star formation, or because of the energy released from massive stars exploding periodically, which prevented the gas from condensing to create new stars.

How the early universe came to be known.

The JADES program is geared towards searching for the oldest galaxies that existed when the universe was younger than 400 million years old. By examining these ancient galaxies, astronomers can investigate how star formation differed in the early days after the Big Bang compared to current times. This is possible because of redshift, which describes how the light from faraway galaxies is stretched to longer wavelengths and redder colors due to the expanding universe. By measuring a galaxy’s redshift, its distance and, consequently, its age can be determined. Before Webb’s observatory, only about thirty galaxies were observed with a redshift of 8 or higher, when the universe was younger than 650 million years old.

The gold standard for determining redshift involves looking at a galaxy’s spectrum which measures its brightness at a myriad of closely spaced wavelengths. However, a good approximation can be determined by taking photos of a galaxy using filters that each cover a narrow band of colors to get a handful of brightness measurements. This is referred to as photometric redshifts and allows researchers to estimate the distances of many thousands of galaxies at once. Kevin Hainline and his colleagues made use of the Near-Infrared Camera (NIRCam) instrument on the Webb observatory to identify more than 700 candidate galaxies that existed between 370 million and 650 million years old. This number was far beyond what was predicted prior to the launch of the Webb observatory.

The American Astronomical Society’s 242nd meeting in Albuquerque, New Mexico recently unearthed some fascinating insights into the earliest galaxies in the universe. According to astronomer Kevin Hainline, these galaxies previously appeared as little smudges representing billions of stars at the start of the universe. However, now, with new technology, it has become possible to spot extended objects with visible structure. This means that astronomers have been able to observe groupings of stars being formed only a few hundred million years after the Big Bang. Fellow astronomer George Rieke added that these new discoveries reveal that star formation in the early universe is much more intricate than previously thought.