An artist’s conception shows the James Webb Space Telescope in orbit around the Sun, a million miles from earth. Credit: NASA-GSFC, Adriana M. Gutierrez (CI Lab)
Since early July, the James Webb Space Telescope has provided Earthlings with stunning images of nebulae (star-forming regions), a galaxy cluster that appeared in It’s A Wonderful Life and thousands of galaxies in deep-field images, all with clarity and detail never before possible. Most recently, NASA has touted the telescope’s first images of Mars.
But the Webb Telescope – JWST for short – is more than just an expensive camera that took 25 years to build. Positioned in orbit around the Sun, a million miles from Earth, JWST helps scientists peer farther into space and billions of years back in time to more clearly observe the universe in its early stages of formation.
Physics and astronomy professor Allison Strom. Credit: Northwestern University
Closer to home, Northwestern University physics and astronomy professor Allison Strom leads one of the first scientific projects to use JWST: the CECILIA Survey, which had 40 hours of research time on the new celebrity telescope in early July.
The survey utilized an instrument called NIRSpec (for Near-InfraRed Spectrograph), which took images of around 30 galaxies that were forming 10 billion years ago, during a time period referred to as “cosmic noon,” several billion years after the Big Bang.
“These are like teenage galaxies going through a time of rapid change and rapid growth, and what happens to them during this time in their life essentially will set what happens for the rest of their life,” explained Strom, whose research focuses on how galaxies grow and change. Studying relatively young galaxies in this 10-billion-year “lookback time” provides a baseline for understanding how older galaxies developed and why some are different from others. (When a telescope views objects that are, for example, 10 billion light-years away, it is actually seeing them as they were 10 billion years ago.)
The CECILIA Survey team will use JWST data to ascertain each galaxy’s chemical makeup — the presence and quantity of oxygen, sulfur, silicon and other elements that are emitted as stars evolve and when they die. The amount of these elements helps reveal the rate and speed of star formation in a galaxy, which in turn sheds light on how the galaxy formed and grew. Strom likens galaxy chemistry to DNA, which provides information about the origins of living things and can also predict some aspects of their development.
Tracking galaxies in a rainbow
CECILIA — an acronym for Chemical Evolution Constrained using Ionized Lines in Interstellar Aurorae — detects specific elements using spectroscopy, a method of viewing the amount of light coming from an object such as a planet, star or galaxy at different colors. “Light” in this sense means wavelengths of varying frequencies on the electromagnetic (EM) spectrum, only a small portion of which can be seen by the human eye.
EM radiation includes radio waves, microwaves, infrared radiation, visible light (what we see), ultraviolet light, x-rays and gamma rays. JWST looks at near-infrared and mid-infrared radiation in the universe.
Credit: NASA and the Space Telescope Science Institute (STScI)
Each element on the periodic table has a unique spectrum that expresses itself across a band of rainbow-colored light marked with dark absorption lines. A spectrum can also be viewed in the reverse: a black band with colored emission lines (the “ionized lines” in CECILIA’s name).
JWST’s distance from the moon and earth, as well as its exclusive focus on infrared light, makes it a more sensitive tool than ground-based telescopes for capturing the spectra of distant galaxies, according to Strom.
Credit: NASA and the Space Telescope Science Institute (STScI)
“Because they are very far away, they’re also rapidly moving away from us due to the expansion of the universe, so all of their features get red-shifted, they get stretched into longer wavelengths, and then you have to look in the infrared,” she said.
The NIRSpec instrument that CECILIA used is similar to a camera but with 250,000 tiny “microshutters,” each measuring about the width of a human hair. NIRSpec can collect spectra on up to 100 objects at once, so it is significantly faster than observing just one object at a time through a more traditional telescope.
Gwen Rudie, the co-principal investigator with Strom on the CECILIA Survey, spent about 100 hours selecting galaxies with a wide range of properties for NIRSpec to view. Those galaxies will serve as a baseline for building a new tool to help astronomers measure the chemistry of other galaxies in the same 10-billion-year lookback time and even earlier.
“The goal of CECILIA is to build this tool which we can apply to thousands of galaxies at cosmic noon and many more galaxies all the way out to the epoch of reionization, the very first galaxies,” said Rudie, a staff astronomer at the Carnegie Institution for Science in Pasadena, California. “By doing so we hope we can chart the buildup of heavy elements in the universe that signal this growth of galaxies and and how they change over time to look like all the diversity of galaxies we see at modern day.”
Celebrating a stellar pioneer
The CECILIA Survey’s name honors Cecilia Payne (later Payne-Gaposchkin), the astrophysicist who first determined that the sun and earth had different chemical makeup. English-born Payne studied science at Cambridge University, completing her studies in the early 1920s, though she was denied a degree because she was a woman. She accepted a postgraduate fellowship with the Harvard College Observatory, embarked on her doctoral dissertation, and in 1925 became the first woman to earn a Ph.D. in astronomy from Radcliffe, the women’s college of Harvard.
Cecilia Helena Payne-Gaposchkin (1900-1979), astrophysicist at Harvard College Observatory, determined that stars and planets had different chemical “DNA.” Credit: Smithsonian Institution Archives, Accession 90-105, Science Service Records, Image no. SIA2009-1326
Backed by her extensive analysis of stellar spectra, Payne’s doctoral thesis proposed that helium and especially hydrogen – the lightest and most abundant elements in the universe – were the main components of stars, contradicting long-held beliefs that planets (which are largely composed of heavier elements) and stars were the same.
A prominent Princeton astronomer, Henry Norris Russell, disputed her discovery but four years later realized for himself that Payne was correct. More than three decades later, Payne had not only become Harvard’s first female faculty member but she became the first woman to be appointed chair of Harvard’s astronomy department, having spent years teaching and conducting research – much of it on variable stars with her husband, astronomer Sergei Gaposhkin – without the status or salary of a tenured professor.
“I think she’s definitely one of these really big giants of the field that a lot of women look up to,” Strom said, “and given the connection to learning about what things are made of, we were just really excited to pay homage to here.”
In 1977, Payne was vindicated when she became the first woman to receive a prestigious prize named for her former critic: the Henry Norris Russell Lectureship, a lifetime achievement award for astronomical research conferred by the American Astronomical Society. (Russell had died 20 years prior.)
Rudie adds that the project’s name not only honors women like Payne – early astronomy and astrophysics pioneers who received little to no credit for their work – but also symbolizes her and Strom’s desire to make astronomy a more inclusive environment for all people.
“A hundred years ago women weren’t allowed to have novel ideas and participate in science,” Rudie said. “Women are allowed now, but there’s still barriers and a lot of progress to be made. We are trying our best to open the gates wider to other communities that have been excluded and are still being excluded today.”
Galactic DNA: What’s the point?
In a world that seems to be withering from climbing temperatures and collapsing under the weight of inflation, some might wonder what galaxy formation has to do with them and why anyone but the most devoted science nerd would be interested in it.
Strom points out science can be an expression of human creativity, and she believes more kids might be interested in pursuing science if they were exposed to the creative aspects of it. Additionally, many scientific instruments have evolved for everyday use, including digital cameras and medical scanners whose roots began in astronomical imaging. Most importantly, she said, science research like the CECILIA Survey contributes to our knowledge of who we are and how we ended up here, starting from the Big Bang through to the formation of our galaxy, our solar system and our home planet.
“If you want to know where we came from, knowing where the Milky Way came from is really a big part of that story,” Strom said, “so understanding galaxies is really one of the central questions about our own origin and our own place in the universe.”
Related: The James Webb Space Telescope has stirred some controversy over its namesake, and some astronomers – including two from the Chicago area – are demanding that NASA change the device’s name.
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