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Astrophysicist Samuel Harvey Moseley Jr. ’72 worked on a key component of the James Webb Space Telescope, the most powerful telescope ever launched into space.
By Amy Martin
amuel Harvey Moseley Jr. ’72 wasn’t too nervous when NASA launched the James Webb Space Telescope—the largest and most powerful ever—into space on Christmas Day, 2021.
But the astrophysicist, who conceived of and led the development of Webb’s microshutter array, a key technological component that enables the telescope to take photographs of deep space, did hold his breath a few weeks later as the otherworldly looking contraption unfolded its giant mirror wings far from Earth.
“I knew where the complexities were in the system, and I knew the steps that were most critical for the microshutters. It turns out the biggest mechanical impulse they get is not during the launch but when the side wings on the mirror are released,” said Moseley, now the vice president for hardware engineering at a New Haven-based quantum computing startup, Quantum Circuits.
Moseley watched the progress with his friend and longtime colleague John Mather, the senior project scientist for Webb. The two worked together on Webb beginning in the late 1990s and, before that, on the Cosmic Background Explorer mission (COBE), which confirmed the Big Bang theory and for which Mather won a Nobel Prize.
“We were trying to see how it was going, and he’s absolutely calm. He said, ‘We did everything we needed to do. We found everything we could find, and we tested everything. We have to be OK with that,’” Moseley recalled Mather saying.
Mather had every reason to trust Moseley’s design for the microshutters, a series of 250,000 tiny windows with shutters that open and close to allow the telescope to record and measure up to 100 distant galaxies at once, including some of the very first galaxies formed after the Big Bang.
For decades, Moseley had been the figure-it-out guy at NASA’s Goddard Space Flight Center—the one who could solve complex mathematical equations and invent the technologies to measure and record ever deeper into the cosmos. And in January, he was awarded the National Academy of Sciences’ 2022 James Craig Watson Medal for his contributions to the development of astronomical detectors that have “profoundly changed our understanding of the universe.”
Once again, one of Moseley’s designs is working: On March 16, NASA released stunning test images of a star (called 2MASS J17554042+6551277) with other galaxies and stars clearly visible behind it. The images, Webb deputy telescope scientist Marshall Perrin told CNN, “are focused together as finely as the laws of physics allow.”
Webb wasn’t launched just to produce pretty pictures of stars. The telescope will possibly bring into focus the very first generation of objects to form after the Big Bang. It might answer all sorts of interesting questions, Moseley said, like “‘How do galaxies form and grow?’ ‘How do supermassive black holes in the cores of galaxies grow over time?’”
The working theory is that there are mergers of galaxies over time, an absorption of one galaxy by another. Understanding this process can teach us about how, 13.8 billion years after the Big Bang, our world came to be.
First images from the Webb Telescope, July 2022
For image details/descriptions, click here. Credits: NASA, ESA, CSA, and STScI
Long before he figured out ways to detect the earliest and farthest corners of the universe, Moseley tinkered with broken things.
He attributes his storied career to equal parts hard, focused work and a healthy dose of good fortune. The hard work started early. Growing up on his family’s farm in rural southern Virginia, Moseley spent his childhood fixing farm equipment and working at the general store his great-grandfather opened after the end of the Civil War.
“I learned to fix mechanical things very young,” Moseley said. “When you’re fixing something mechanical, you need to think about the problem and take a fairly scientific approach to solving it, or else you’re going to spend a lot of time doing the wrong thing.”
Moseley describes his hometown as “one of those places where nobody comes in, and nobody comes out.” But young Moseley, a voracious reader with an interest in astronomy, did.
An assistant principal at the local high school recognized the potential in his teenage pupil and suggested Moseley try to find a more challenging school environment. So Moseley applied and was awarded a scholarship to a private all-boys school in Alexandria, Virginia, setting him on a path to quite literally reach for the stars.
But first, to quote the film Good Will Hunting, he “had to go see about a girl.” Moseley had been dating his childhood sweetheart, Sarah, throughout high school, and upon graduation, she had decided to attend Connecticut College for Women. It was 1969, and the school had just announced it would be changing its name and enrolling men for the first time. So Moseley followed Sarah to Conn.
“I had just come from an all-boys school, so why not attend an all-girls college?” Moseley joked. “But it was fun. All the guys lived in one dorm and we had a very congenial group.”
An enthusiastic mathematician, Moseley studied math at Conn, but he also found a home in the Physics Department. Moseley’s math skills translated well to physics, and his professors, particularly David Fenton and Robert Brooks, took an interest in him, providing him with opportunities to explore beyond the curriculum. He also ran the labs, where, of course, he “fixed all the broken stuff.”
Moseley graduated from Conn in just three years. He and Sarah, still very much in love, got married, and together they “took off to the wilds of the Midwest” so Moseley could pursue a doctorate in astrophysics at the University of Chicago.
THE ULTIMATE BABY PICTURE
Part of Moseley’s success is timing. The first satellite to orbit Earth, Sputnik, launched in 1957, when Moseley was a boy. In 1961, the first astronauts took flight, and in July of 1969—as Moseley left for Conn—Neil Armstrong took “one small step” onto the moon and famously declared it “one giant leap for mankind.” Space was the new frontier, and there was much to explore.
Moseley arrived at the University of Chicago in the early days of far-infrared astronomy, which allowed scientists to observe and measure longer wavelength light and peer deeper into space than ever before.
“It was all new. We were doing the very first measurements … on Uranus and Neptune, and found that Neptune has a strong internal heat source and Uranus doesn’t, and that wasn’t known before,” Moseley said.
The team was first working with a small telescope on a Learjet, then moved on to the Kuiper Airborne Observatory, a converted military cargo plane capable of flying above almost all of the infrared-absorbing water vapor in the Earth’s atmosphere.
Through trial and error in a completely new field, Moseley and his colleagues developed new systems and technologies to make rapid improvements in the measurement systems.
“You sort of invented how to do everything without even knowing you were doing it. If something came up that needed to be done, you did it, and then after a while, that became the way it was done,” said Moseley, who added that “being able to invent and make new things with technology is almost like having a superpower.”
Now fully hooked on the thrill of cosmic discovery, Moseley joined NASA’s Goddard Space Flight Center to work on the COBE project. The goal was to measure cosmic microwave background radiation, or electromagnetic radiation that comes from every direction—a remnant from an early stage of the universe.
“In other words, we were trying to take the ultimate baby picture of the universe,” Moseley said.
Leading the mission was a young John Mather. “I had found myself in the best possible place in the world, with a wonderful collaborator. He and I worked so well together,” Moseley said.
Mather, a self-described “theoretical experimentalist,” would come up with grand theories of experiments he thought possible. Moseley would bring the theories to life.
“If there was a question, we’d chat about it and I would go come up with a proxy for that experiment to see what we could learn, and we’d bat it back and forth,” Moseley said. “He’d have these big ideas, and I’d figure out what you needed to have in your hands to make it possible.”
Moseley had also arrived at NASA with an independent grant for continued work on infrared astronomy, which would eventually prove very useful for the COBE project after the X-ray guys from down the hall came knocking on the door. It was a bit of serendipity that led Moseley to one of his most influential inventions, the X-ray microcalorimeter.
In preparation for the next generation of major X-ray telescopes, the X-ray team was looking for a semiconductor that would work better for detecting X-rays than the silicon diode—an electrical component that allows the flow of current in only one direction—they had been using. The COBE team was testing different diodes for their various instruments at the time, and the X-ray team wanted to know if any of them would work better for their telescopes.
The answer, Moseley determined, was no. But he had another idea.
“I realized I had actually solved this problem before. Someone had once asked me about the minimum amount of laser energy you could detect with a thermal detector, which absorbs radiation and records changes in temperature, so I did that calculation.”
Moseley found the calculation in his office drawer, and the next day, he brought it down the hall to the X-ray team and explained that since detecting the energy from a single X-ray is exactly like detecting the little pulse of laser energy, using thermal detectors would work about 100 times better than using silicon detectors.
The team put Moseley in touch with Dan McCammon, a professor of physics at the University of Wisconsin, and together they secured funding to rapidly develop the microcalorimeter technology to transform X-ray spectroscopy. Today, the technology they pioneered is being used for a wide range of applications, from dark matter detection to nuclear nonproliferation to quantum computing.
The COBE mission, which operated from 1989 to 1993, was a huge success. Two key measurements confirmed the Big Bang theory with extraordinary accuracy. Mather and another team member, George Smoot, would go on to win the Nobel Prize
in Physics in 2006. At the time, the Nobel Committee wrote, “The COBE project can also be regarded as the starting point for cosmology as a precision science.”
For his role in the mission, Moseley was awarded the Connecticut College Medal, the institution’s highest honor, in 1992. After COBE, Moseley began working on the Spitzer Space Telescope, an infrared telescope that was a successor to the airborne astronomy he had done in graduate school. Spitzer could be cooled to almost absolute zero so that its own heat wouldn’t interfere with its measurements, making it more than 100 times more sensitive than the previous iteration. Moseley was the instrument scientist for the mission, and he led the development of the telescope’s Infrared Array Camera.
Then, in the late 1990s, the James Webb project began to take shape. Dubbed the successor to the fabled Hubble, the goal of Webb was to use infrared astronomy to view much older, more distant and fainter objects—ideally the very first objects in the universe after the Big Bang.
But there was a problem—a big problem—that needed to be solved.
“We needed a spectrometer to allow us to observe these large numbers of very, very distant galaxies at one time; there just isn’t enough time to look at each one sequentially,” Moseley said.
Mather was leading the science team for Webb, an international partnership between NASA, the European Space Agency (ESA) and the Canadian Space Agency, and Moseley decided to take on the challenge, despite an initial hesitation. (“I’ve got plenty to do,” he told a fellow scientist who initially approached him. “No, you should do this,” his friend told him.)
Moseley realized that what was needed was a way to open up a tiny window focused on each galaxy that would block the light from other nearby objects, and he set to work designing the microshutter array, a series of tiny shutters that measure about the width of a human hair.
The final iteration, built in Munich by the ESA, is a set of four arrays, each containing more than 62,000 shutters that focus the attention of an infrared camera on a very specific object. Because the galaxies are so distant, it will take a long exposure time to get an image, but the microshutters allow the telescope to look at 100 different objects simultaneously, increasing the speed of scientific discovery by a factor of 100.
While initial test images are impressive—“focused together as finely as the laws of physics allow”—the best is yet to come.
The telescope recently finished cooling to operating temperature, and the instruments are now being calibrated. The first scientific images are expected this summer.
Webb also features a special aperture for exoplanets, planets that orbit stars other than the sun. Studying exoplanets may someday help answer one of humanity’s greatest questions: Are we alone?
On that question, Moseley is torn. On the one hand, it’s very possible that Earth is an anomaly with a specific set of critical, unique systems that statistically just aren’t probable anywhere else in the universe. On the other hand, the universe is a very big place.
“Existence itself is a pretty oddball thing, isn’t it?” he mused.