With the help of the joint NASA/European Space Agency/Canadian Space Agency James Webb Space Telescope (JWST), scientists are peering deep into the universe and uncovering secrets previously hidden from visible and X-ray telescopes. The JWST Advanced Deep Extragalactic Survey (JADES) used Webb’s incredible deep field sensing capabilities to create a deep field that shows more than 45,000 galaxies and unlocks some of the secrets of the early universe.
Another team used Webb’s immense sensitivity to infrared light to peer behind the thick dust within the bars of a barred spiral galaxy. Behind the dust within the bars of the galaxy were hundreds of bubbles of gas where hot young stars are forming and growing.
JADES data reveals 45,000 galaxies, unlocks secrets of early universe
In the fields of astrophysics and cosmology, one question has existed in the minds of scientists for centuries: when did our universe form and how did the first stars and galaxies form? In recent decades, various telescopes, such as the Hubble Space Telescope and ground-based observatories, have been used to create huge mosaics of portions of the sky called deep fields. Hubble’s 1995 Deep Field is among the most popular images of our universe ever created, and subsequent deep fields have allowed scientists to peer deeper and deeper into our universe by increasing exposure times.
However, Hubble is only so powerful and is limited by its 2.4-metre mirror. Webb’s mirror, launched with the observatory in December 2021, is nearly three times the size of Hubble’s mirror, at 6.5 metres. Webb’s mirror’s larger size, powerful instruments, and infrared sensitivity allowed him to create some of the deepest deep fields of all time, with one of JADES’ first deep fields pinpointing galaxies that existed when the universe was less than 600 million years old – and an incredible feat given Webb’s young age.
JADES is one of the largest programs allotted time in Webb’s freshman year of science, with 32 days of that freshman year devoted to gathering data for JADES and creating incredible deep fields. Much of the JADES data is yet to come, but the team is already making groundbreaking discoveries that will change astrophysics and cosmology forever.
With JADES, we want to answer many questions, such as: how did the first galaxies assemble? How fast did stars form? Why do some galaxies stop forming stars? said JADES co-lead Marcia Rieke of the University of Arizona.
Using Webb’s data, a team within JADES, led by Ryan Endsley of the University of Texas at Austin, studied galaxies that existed between 500 million and 850 million years after the formation of the universe. This specific period of time, which is referred to as the epoch of reionization, is when much of the gas that clouded the energetic light in the early universe disappeared in a process called reionization. Scientists aren’t entirely sure what led to the reionization of the gas, but they believe supermassive black holes or young galaxies may have played a significant role in the reionization.
Endsley et al. used Webb’s near-infrared spectrograph (NIRSpec) to find and study galaxies that existed during the epoch of reionization. NIRSpec specifically looked for star formation signatures and was able to identify many of these signatures.
Almost every single galaxy we’re finding shows these unusually strong emission line signatures that indicate intense recent star formation. These early galaxies were very good at making hot, massive stars, Endsley said.
You are looking at over 45,000 galaxies.
This image was taken as part of the JWST Advanced Deep Extragalactic Survey (JADES), a massive science program that is revolutionizing what we know about galaxies in the early universe: https://t.co/5gqntO0C4S
Here are the highlights pic.twitter.com/8VqYlmvtDK
NASA Webb Telescope (@NASAWebb) June 5, 2023
But how did these young stars influence the reionization of the gas?
The stars forming within the star-forming regions identified by NIRSpec were massive and extremely luminous, meaning they emitted extraordinarily large amounts of ultraviolet light. This ultraviolet light would ionize the gas surrounding the stars, and given the large numbers of these young stars within galaxies in the early universe, Endsley et al. they believe these young galaxies could be the main driver behind the reionization of gas during the reionization epoch.
Furthermore, Endlsey et al. found that these young galaxies probably experienced periods of extreme star formation separated by periods of slow star formation. Periods of extreme star formation would likely have been caused by galaxies absorbing massive clumps of gas and other materials used up during the star formation process. On the flip side, the massive stars within these galaxies may have exploded rapidly, which would have injected large amounts of energy into their surroundings and prevented the gas from condensing and forming new stars.
As mentioned above, the deep fields created by programs like JADES allow scientists to peer into the earliest periods of the universe and have given scientists the ability to discover galaxies that existed when the universe was less than 600 million years old. Several teams within JADES are specifically looking for galaxies that existed when the universe was less than 400 million years old. Finding and studying these galaxies will allow scientists to explore features of the early universe, especially how star formation differed in the early universe compared to what they see now.
However, how do scientists determine how far away a galaxy is and when it existed in the universe?
Whenever light is emitted from a cosmic object, that light travels in waves throughout the universe. As the universe is expanding, these light waves stretch into longer wavelengths and become redder. This phenomenon is called redshift, and when an object’s redshift is measured, scientists are able to determine how far away it is and when it existed. An object’s redshift is typically measured by looking at the spectrum of a galaxy, which shows a collection of wavelengths representing the contents of the galaxy. However, redshift can also be measured by imaging a galaxy with a variety of filters that cover narrow bands of color, resulting in images with varying levels of brightness. The latter method allows researchers to determine the redshifts of several thousand galaxies simultaneously.
Led by Kevin Hainline of the University of Arizona, a team of JADES scientists used Webb’s near-infrared camera (NIRCam) to obtain measurements of the redshift, known as photometric redshifts, of galaxies in the inside of JADES data. NIRCam has identified over 700 galaxies that could have existed when the universe was between 370 million and 650 million years old.
Previously, the first galaxies we could see looked like little specks. Yet those spots represent millions or even billions of stars at the beginning of the universe. Now we can see that some of them are actually extended objects with visible structure. We can see clusters of stars being born just a few hundred million years after the beginning of time, Hainline said.
Finding star formation in the early universe is much more complicated than we thought, Rieke said.
Before Webb, discovering and measuring redshift galaxies was extremely difficult, with only a few dozen galaxies observed with a redshift greater than eight (which is equivalent to when the universe was less than 650 million years old). . In less than a year of scientific observations, Webb and JADES have already discovered thousands of galaxies with redshifts greater than eight.
JADES results were presented at the 242nd meeting of the American Astronomical Society.
Discovering the secrets behind the dust of NGC 5068
Webb continues to uncover the secrets of our universe by peering behind the dusty bars of the barred spiral galaxy NGC 5068. Using NIRCam and the mid-infrared (MIRI) instrument, Webb imaged NGC 5068 in both the near and mid-infrareds, giving scientists a glimpse into the depths of the barred galaxy. Webb envisioned the galaxy as part of a campaign to develop a database of stellar nurseries within nearby galaxies.
NGC 5068 is located about 20 million light-years away in the constellation Virgo and has long been thought to host stellar nurseries, areas of hot gas and dust where star formation typically occurs. Stellar nurseries not only trigger star formation within them, but also serve as places where hot, young stars grow and develop into main-sequence stars.
Areas of star formation within galaxies are of interest to scientists due to their relevance to several fields of cosmology and astrophysics. Star formation, as discussed above, is thought to have changed dramatically throughout the history of the universe, so understanding star formation during different periods of our universe’s history may prove extremely important in determining how the universe was shaped in what it is today. Additionally, Webb’s incredible observations can be used in tandem with observations from other telescopes such as the Hubble Space Telescope and the Atacama large millimeter/submillimeter array to create a detailed look at the star formation process.
Here is NGC 5068 as seen only by Webb’s Mid-Infrared Instrument (MIRI). This image highlights dust and gas containing newly formed star clusters. Look closely to find asteroid trails (shown as tiny blue-green-red dots) that are easier to see here, as the stars aren’t as bright in the mid-infrared. pic.twitter.com/Wm4GvUB7FF
NASA Webb Telescope (@NASAWebb) June 2, 2023
Webb’s infrared sensitivity allows him to see beyond the dust within NGC 5068, allowing the observatory to identify stellar nurseries and the processes and environments that enable star formation. With the combined capabilities of MIRI and NIRCam, Webb is able to observe star formation processes as they occur and the swirling structures of the environments surrounding the stellar nurseries where star formation occurs.
(Main image: (top left) Webb’s JADES deep field of GOODS-South, (bottom right) Webb’s image of NGC 5068. Credits: (top left) NASA/ESA/CSA/ Brant Robertson/Ben Johnson/Sandro Tacchella/Marcia Rieke /Daniel Eisenstein/Alyssa Pagan, (bottom right) ESA/Webb/NASA/CSA/J. Lee/PHANGS-JWST Team)
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