UArizona Astronomers to Help NASA's James Webb Space Telescope Peer into Space's Past

Artist conception of the James Webb Space Telescope.

Artist conception of the James Webb Space Telescope. A tennis-court-sized shield will keep the extremely sensitive infrared detection instruments out of sun's rays.

NASA GSFC/CIL/Adriana Manrique Gutierrez

NASA's James Webb Space Telescope, which will look farther back in the history of the universe than any telescope before it, has arrived in French Guiana, where it will be readied for launch on Dec. 18. University of Arizona researchers will provide leadership for two of the instruments onboard.

The worlds largest and most complex space science observatory will now be driven to its launch site, Europe's Spaceport in Kourou, where it will begin two months of operational preparations before its launch. At the launch site, the telescope will be stowed folded inside the nose cone on top of an Ariane 5 rocket, designed to protect the space observatory from the air blast and the drastic drop in temperature as the rocket lifts off and leaves Earth behind in the span of a few minutes.

UArizona husband-and-wife researchers Marcia and George Rieke, who both have leadership roles in the James Webb Space Telescope, have worked toward this moment for two decades. However, because of the launch site's remote location, access to the site is extremely limited, and even the Riekes will have to attend the launch virtually with their research teams at UArizona.

Though it is often billed as the "successor" to NASA's Hubble Space Telescope, the James Webb Space Telescope – or Webb, as astronomers like to call it – is an entirely new and different beast, according to Marcia Rieke, a Regents Professor of Astronomy at the University of Arizona's Steward Observatory.

Marcia Rieke

Marcia Rieke

"The Hubble and Spitzer Space Telescopes revolutionized our understanding of the cosmos," she said. "But with Webb, we'll be able to probe galaxies much closer to the Big Bang than ever before."

Marcia Rieke is principal investigator for the Near Infrared Camera, or NIRCam, which sits at the heart of the Webb Telescope. She led the development of the instrument, which was conceived to carry out the telescope's original purpose: to discover what astronomers refer to as "first light" galaxies at the moment of their formation in the very early universe.

"We can currently see galaxies back to 500 to 600 million years post-Big Bang, nearly 13 billion years ago," Marcia Rieke said. "And even though the universe was so young at that time, the things we see still look pretty familiar – lots of stars have formed, there are supermassive black holes, quasars and so on.

"However, logic dictates that at some point during the first few hundred million years, these familiar-looking objects must have come from somewhere and evolved," she explained. "After all, galaxies don't spring up from nothing, virtually overnight."

Her team will work with the Webb spectrometer team to peer into this formative stage of the familiar present-day universe. Because the universe is expanding, light from the earliest galaxies has been stretched, or "redshifted," from visible light into longer wavelength infrared light, which is invisible to the human eye. NIRCam will be able to visualize infrared light, making the instrument essential to examining the early phases of star and galaxy formation, and studying the shapes and colors of distant galaxies. 

George Rieke

George Rieke

George Rieke, also a Regents Professor of Astronomy, is science team lead for the Mid-Infrared Instrument, or MIRI, built by a consortium of European scientists and engineers and NASA's Jet Propulsion Lab. MIRI was added to Webb to expand the telescope's reach even farther into the infrared spectrum and enable many additional investigations. Two other instruments, supplied by the European and Canadian Space Agencies, round out Webb's scientific package.

The University of Arizona's leadership of two of Webb's core instruments is a family affair for the Riekes, but it also reflects the university's 60 years of leadership in infrared astronomy. The university's strength in this field allowed it to successfully compete for observing time on the new telescope. The combined time allocated by NASA to the two UArizona instrument teams and other UArizona astronomers accounts for 13% of the total observing time awarded, giving UArizona more time than any other astronomy center in the world.

"The university's contributions to the design and development of advanced instrumentation aboard the JWST is a testament to our bold, inventive approach to astronomy," said Elizabeth "Betsy" Cantwell, UArizona senior vice president for research and innovation. "This telescope has the potential to answer some truly wondrous and fundamental questions about the characteristics of faraway planets and the origins of the universe itself; I am confident it will transform our understanding of the cosmos, and proud of the role of University of Arizona researchers in that feat."

A sensor array for the NIRCam instrument, designed and tested by Marcia Rieke's research group at Steward Observatory.

A sensor array for the NIRCam instrument, designed and tested by Marcia Rieke's research group at Steward Observatory.

Marcia Rieke

Bigger, Colder and Sharper

Webb is revolutionary for astronomy because it will be both cold and large.

"Getting into space is critical for infrared astronomy," said George Rieke, explaining that while observing in the infrared with ground-based telescopes is possible, the effort is plagued by heat "noise" coming from the instrument itself, as well as the atmosphere.

"Astronomical sources have to be detected against this overwhelming and highly variable foreground, so it's a bit like trying to find a match in a blast furnace," he said.

Ground-based telescopes can't be cooled down enough to get rid of their heat emission, he explained, as water would condense on them and blind them. However, in the vacuum of space, this is not a problem, allowing the Webb Telescope to shed its heat energy until it reaches a temperature of minus 234 degrees Celsius, or minus 390 degrees Fahrenheit. A tennis-court-sized sunshade shields the telescope from the heat emanating from the sun, Earth and moon. 

Previous infrared space telescopes, such as the Spitzer Space Telescope, have also worked this way, but compared to Webb, Spitzer was tiny – just 34 inches in diameter, compared to Webb's 21 feet. Not only does Webb's huge size boost its sensitivity, it also makes the images captured by the telescope much sharper. However, 21 feet is too much to fit into any rocket cone. Therefore, Webb will be folded up to be as slim as possible, similar to a closed umbrella.

Towering more than 150 feet above the ground and overlooking murky, shallow waters of an expansive bay on the Atlantic coast, the Ariane 5 rocket that will carry Webb into space weighs 780 tons. Its two boosters stand more than 100 feet tall, each packing 238 metric tons of solid propellant. Once in space, Webb will unfold, its instruments will be thoroughly checked and calibrated, and the mirror will be adjusted to optical perfection. This happens during a six-month period after which the telescope will be a million miles from Earth, four times farther away than the moon. This special point in space will allow Webb to fly effortlessly with the Earth around the sun, making it possible for the telescope to radio its huge amount of data back to Earth.

The worldwide astronomical community will be nervously watching Webb's journey at every stage, the Riekes said.

"Anyone asking us astronomers what we want to do with Webb would be greeted by an enthusiastic chorus of excited voices," George Rieke said.

Veterans in Infrared Astronomy

The Riekes are veterans in the infrared astronomy world, and Webb is not the first space telescope mission for them. Marcia Rieke was deputy principal investigator to UArizona professor Rodger Thompson on the NICMOS instrument installed in the Hubble Space Telescope in 1997. George Rieke led the development of the Multiband Imaging Photometer, a far-infrared instrument on NASA's Spitzer Space Telescope, which launched in 2003.

"The gains that Webb gives us over Spitzer, which until now has been the most powerful space infrared telescope, are nearly 100 times in sensitivity, nearly 100 times in angular resolution element, and, with modern arrays of infrared detectors, more than 100 times in number of pixels," George Rieke said.

Technicians and engineers work on the James Webb Space Telescope, preparing its sunshield to be folded.

Technicians and engineers are seen working on the James Webb Space Telescope in January 2021, preparing its sunshield to be folded.

Northrop Grumman

Marcia Rieke added: "Making full use of such an advance might boggle astronomers' imaginations, but not for our local astronomers, who saw the potential to make huge leaps in understanding scientific puzzles they had pursued for years, from the formation of supermassive black holes and emergence of the first galaxies in the universe, to the growth of young stars and the properties of exoplanets resembling our own solar system."

University of Arizona President Robert C. Robbins said George and Marcia Rieke embody the University of Arizona's spirit of determination.

"At a time when infrared astronomy was widely dismissed as being too difficult, they insisted on pushing the technology," Robbins said. "Driven by the discoveries they foresaw, they kept chipping away at the challenges, and in the process, they helped establish infrared astronomy – one of astronomy's most fruitful subdisciplines – right here in Tucson."

The James Webb Space Telescope is an international partnership of NASA, the European Space Agency and the Canadian Space Agency, with contributions from 26 research organizations, three space agencies and 11 countries. Partners include Goddard Space Flight Center, the Jet Propulsion Laboratory, Space Telescope Science Institute, Northrop Grumman, EADS–Astrium and Raytheon.

Bill Ochs, Webb project manager at NASA's Goddard Space Flight Center, had this to say about the achievement of launching the largest and most advanced telescope ever put into space: "After completing the final steps of the James Webb Space Telescope's testing regimen, I can't help but see the reflections of the thousands of individuals who have dedicated so much of their lives to Webb, every time I look at that beautiful gold (telescope) mirror."