Webb unveils the secrets of the early universe via deep field, peers into stellar nurseries

by Haygen Warren

With help from the joint NASA/European Space Agency/Canadian Space Agency James Webb Space Telescope (JWST), scientists are peering deep into the universe and uncovering secrets that were previously hidden from visible and X-ray telescopes. The JWST advanced deep extragalactic survey (JADES) utilized Webb’s incredible deep-field surveying abilities to create a deep field that shows over 45,000 galaxies and uncovers some of the secrets of the early universe.

Another team took advantage of 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 galaxy’s bars were hundreds of gas bubbles where young, hot stars are forming and growing.

JADES Data Reveals 45,000 Galaxies, Unveils Early Universe’s Secrets

Within 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? Throughout the last few decades, several telescopes, such as the Hubble Space Telescope and ground-based observatories, have been used to create massive 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-meter mirror. Webb’s mirror, launched with the observatory in December 2021, is nearly three times larger than Hubble’s mirror, coming in at 6.5 meters. Webb’s increased mirror size, powerful instruments, and sensitivity to infrared have allowed it to create some of the deepest deep fields of all time, with one of the first deep fields from JADES spotting galaxies that existed when the universe was less than 600 million years old — and incredible feat given Webb’s young age.

A deep field taken by Webb as part of JADES. An area of the sky known as GOODS-South is seen in this image, with over 45,000 galaxies dotting the black sea of space. (Credit: NASA/ESA/CSA/Brant Robertson/Ben Johnson/Sandro Tacchella/Marcia Rieke/Daniel Eisenstein/Alyssa Pagan)

JADES is one of the largest programs to have been awarded time during Webb’s first year of science, with 32 days of that first year being devoted to collecting data for JADES and creating incredible deep fields. Much of the JADES data has yet to come in, but the team is already making groundbreaking discoveries that will change astrophysics and cosmology forever.

“With JADES, we want to answer a lot of questions, like: How did the earliest galaxies assemble themselves? How fast did they form stars? Why do some galaxies stop forming stars?” said JADES co-lead Marcia Rieke of the University of Arizona.

Using data from Webb, a team within JADES, led by Ryan Endsley from the University of Texas at Austin, investigated galaxies that existed between 500 million and 850 million years after the formation of the universe. This specific time period, which is referred to as the epoch of reionization, is when much of the gas that clouded 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 that either supermassive black holes or young galaxies may have had a significant hand in the reionization.

Endsley et al. used Webb’s near-infrared spectrograph (NIRSpec) to find and study the galaxies that existed during the epoch of reionization. NIRSpec specifically searched for signatures of star formation and was able to identify several of these signatures.

“Almost every single galaxy that we are finding shows these unusually strong emission line signatures indicating intense recent star formation. These early galaxies were very good at creating hot, massive stars,” Endsley said.

But how did these young stars influence the reionization of gas?

The stars forming within the regions of star formation NIRSpec identified were massive and extremely bright — meaning they were emitting extraordinarily high amounts of ultraviolet light. This ultraviolet light would ionize the gas surrounding the stars, and given the high amounts of these young stars within galaxies in the early universe, Endsley et al. believe that these young galaxies could be the main driver behind the reionization of gas during the epoch of reionization.

What’s more, Endsley et al. discovered that these young galaxies likely experienced periods of extreme star formation separated by periods of slow star formation. The periods of extreme star formation would’ve likely been caused by the galaxies absorbing massive clumps of gas and other materials that are used during the star formation process. On the flip side, the massive stars within these galaxies could’ve quickly exploded, which would’ve injected high amounts of energy into their surrounding environment and prevented gas from condensing and forming new stars.

As aforementioned, deep fields created by programs like JADES allow scientists to peer into the earliest periods of the universe and have given scientists the chance to discover galaxies that existed when the universe was less than 600 million years old. Several teams within JADES are specifically searching for galaxies that existed when the universe was less than 400 million years old. Finding and investigating these galaxies will allow scientists to explore the characteristics of the early universe, specifically how star formation differed in the early universe when 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 by a cosmic object, that light travels in waves through the universe. Since the universe is expanding, these light waves get stretched 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 observing a galaxy’s spectrum, which displays a collection of wavelengths that represent 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 colors, which produce images with varying levels of brightness. The latter method allows researchers to determine the redshifts of several thousand galaxies all at once.

Compass image of Webb’s deep field of GOODS-South. (Credit: NASA/ESA/CSA/Brant Robertson/Ben Johnson/Sandro Tacchella/Marcia Rieke/Daniel Eisenstein/Alyssa Pagan)

Led by Kevin Hainline of the University of Arizona, a team of JADES scientists employed Webb’s near-infrared camera (NIRCam) to obtain redshift measurements, known as photometric redshifts, of galaxies within the JADES data. NIRCam identified over 700 galaxies that could have existed when the universe was between 370 million and 650 million years old.

“Previously, the earliest galaxies we could see just looked like little smudges. And yet those smudges 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 groupings of stars being born only a few hundred million years after the beginning of time,” said Hainline.

“We’re finding star formation in the early universe is much more complicated than we thought,” Rieke said.

Before Webb, discovering and measuring redshifted galaxies was extremely difficult, with only a few dozen galaxies observed with a redshift above eight (which equates 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 above eight.

The JADES results were presented at the 242nd meeting of the American Astronomical Society.

Uncovering Secrets Held 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 instrument (MIRI), Webb imaged NGC 5068 in both the near-infrared and mid-infrared, giving scientists a look into the depths of the barred galaxy. Webb imaged the galaxy as a part of a campaign to develop a database of stellar nurseries within nearby galaxies.

Composite image of NGC 5068 using MIRI and NIRCam images. (Credit: ESA/Webb/NASA/CSA/J. Lee/PHANGS-JWST Team)

NGC 5068 is located approximately 20 million light-years away in the constellation Virgo and had been thought for some time to house stellar nurseries — areas of hot gas and dust wherein star formation typically occurs. Stellar nurseries not only trigger star formation within them but also serve as places for hot, young stars to grow and develop into main-sequence stars.

Areas of star formation within galaxies are of interest to scientists because of their relevance within several different fields of cosmology and astrophysics. Star formation, as discussed above, is thought to have drastically changed throughout the history of the universe, so understanding star formation throughout the different periods of our universe’s history can prove to be extremely important when determining how the universe was shaped into what it is today. Furthermore, Webb’s incredible observations can be used in tandem with observations from other telescopes like the Hubble Space Telescope and the Atacama large millimeter/submillimeter array to create a detailed look at the star formation process.

Webb’s sensitivity to infrared allows it to see beyond the dust within NGC 5068, allowing the observatory to identify stellar nurseries and the processes and environments that allow for star formation to occur. With the capabilities of MIRI and NIRCam combined, Webb is able to observe star formation processes as they happen and the swirling structures of the environments surrounding the stellar nurseries where star formation occurs.

(Lead image: (top left) Webb’s JADES deep field of GOODS-South, (bottom right) Webb’s image of NGC 5068. Credit: (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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