JWST To Reveal Chemistry Of Ancient Galaxies, Is Taking Data For First Of Six Carnegie-Led Projects

The first of six projects led by Carnegie-affiliated astronomers will, for the next three days, use the James Webb Space Telescope to make some of the most-accurate measurements ever taken of the chemistry of very early galaxies—studying light that traveled 10 billion years to reach us.

Carnegie’s Gwen Rudie and Allison Strom, formerly a Carnegie-Princeton Postdoctoral Fellow, now a Northwestern professor, are heading up the CECILIA project, which will take extremely accurate measurements from a carefully selected set of ancient galaxies in order to understand their compositions and chart the remarkable growth that they experienced in the universe’s youth.

“We think these early galaxies have very, very different chemistry from our own Milky Way and the galaxies that surround us today. And with CECILIA, we will be able to figure out precisely how different they really are,” Rudie explained.

Their project was named in honor of Cecilia Payne-Gaposchkin, who nearly 100 years ago did pioneering work on the chemistry of our Sun. Her findings upended the scientific community’s understanding of the Sun’s composition and she faced unfair criticism for years before her breakthrough work was finally recognized.

Reacting to the first public release of JWST data, Rudie said, “the initial images show us that our project will almost certainly surprise us. We’re excited for the dawn of a new era in astronomy.”

More Carnegie-led JWST Projects:

CECILIA is just one of six first-round JWST projects with lead scientists who are affiliated with Carnegie. They will be using the space telescope’s extraordinary capabilities to gather data through late 2023.

Drew Newman will be pointing JWST at an ancient galaxy about 10 billion light-years from us in order to understand why some galaxies stopped forming stars very early on, even though the universe at the time was a very active place and most galaxies—such as those studied by Rudie and Strom—were just bursting with star formation.

His designated time won’t occur until November or December of next year, but the wait isn’t dampening his excitement about realizing JWST’s tremendous promise for revealing our universe in never-before-seen detail.

"This telescope is an absolutely incredible accomplishment,” he said. “JWST's first deep images and spectra already deliver surprises, they're just a hint of how much we will learn about galaxies' birth and growth.”

Johanna Teske’s first JWST observations are preliminarily scheduled for next February, although they will also be peppered throughout the summer and into the fall.

“In the meantime,” she said, “we can learn from all the incoming data, and our expert colleagues, and be ready to hit the ground running.”

The project her team is working on aims to better understand the most-common type of planet in our Milky Way galaxy—called super-Earths or sub-Neptunes—which mysteriously are not found in our own Solar System.

JWST will allow Teske and her colleagues to try to figure out how much variety there is in the atmospheric makeup of these planets, as well as the phenomena that control this composition—information that could reveal whether these types of planets have conditions that are conducive to life.

“We expect our observations to push the telescope and the instrument we will be using to their limits,” Teske said. “The first results we've seen indicate that they are behaving at least as well as expected and, in many ways, substantially better. This means we will likely uncover even more about small planets than we’d initially anticipated—like whether they have atmospheres that formed via outgassing from their interiors, or whether they are so-called ‘water worlds.’”

Peter Gao will also be deploying JWST to probe exoplanet atmospheres. Next May he will use the revolutionary space telescope to improve our knowledge of a rare type of ultra-low density—think cotton candy—planets, which have masses of only a few times that of Earth, but sizes like those of the giant planets in the Solar System. Gao hopes that JWST will enable him to reveal the underlying explanation for the unusual densities of this mysterious planetary class.

“It's interesting to think about how different my understanding of exoplanets will be between now and next May and how quaint the original models I generated for this planet will look in retrospect,” Gao said.

As a theorist, Gao made advanced predictions of what JWST observations would reveal, including generating synthetic observations. Now, he says the onus is on theorists to explain what the telescope data show.

“The unknown is suddenly so much closer to being knowable, and questions we haven't even thought of are about to be posed. It really feels like my career has just begun,” he added.

By contrast, JWST has been a part of Alan Dressler’s career for more than 25 years. In the mid-1990s, he chaired the committee that led to the space telescope’s conception. Now, he’s part of the instrument team for JWST’s Near Infrared Camera and will be using deep-field images to analyze the star-formation histories of galaxies from the universe’s first hundred million years.

“NIRCam will help us understand how galaxies are built from gas clouds collapsing through gravity to form stars, and how these then collect into larger structures,” he explained.  “My focus will be to see if these infant galaxies have ‘bursty,’ rather than steadily rising or falling, rates of star formation, behavior we expect to be very different in galaxies as they mature.”

Dressler was invited to the Space Telescope Science Institute’s unveiling of the first images and describes the awe of the astronomers in the room at that moment.

“I was blown away by the richness of information,” he said. “It’s one thing to imagine what such data are going to be like when you take a big step like building JWST, but somehow, you’re never quite prepared for where the next journey toward the horizon is going to go. I wouldn’t have said this before, but I now feel confident that JWST will be as big a step for our field as the Hubble Space Telescope has been. We are in for a great adventure.”

Other JWST projects include one from Maria Drout, an Assistant Professor at the University of Toronto and a Visiting Scientist at the Carnegie Observatories, who will explore the origins of the heaviest elements in the periodic table and one from Barry Madore who hopes the space telescope will enable he and former-Observatories Director Wendy Freedman to refine our measurements of the rate at which the universe is expanding, called the Hubble Constant. The Observatories’ Jeff Rich is also a member of a research team that will use JWST to study galaxy collisions and measure how these violent phenomena can create intense bursts of star formation and growth of the supermassive black holes at their centers.

What About Ground-based Telescopes?

Excitement over the JWST’s capabilities has rippled through the astronomy community. But this doesn’t diminish the importance of the next generation of ground-based telescopes, including the Giant Magellan Telescope, currently under construction at Carnegie’s Las Campanas Observatory, for driving future discoveries.

“These large ground-based telescopes will be super complementary to things like James Webb,” explained Observatories Director and Carnegie Science Deputy John Mulchaey.

The optical capabilities of GMT—as compared to the infrared instruments deployed on JWST—will enhance astronomers’ capacity to detect biosignatures such as oxygen in exoplanet atmospheres. Likewise, the difference in mirror size between a space-based and ground-based telescope will enable astronomers to use GMT to characterize the first stars and galaxies detected by JWST with much greater detail.

“This is going to be a super exciting combination,” Mulchaey added.

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