Webb Telescope Launch Could Shift Our Understanding of the Early Universe

“We want to look at those first galaxies growing,” said John Mather, a Nobel Prize-winning astrophysicist and the senior project scientist for the Webb telescope at the National Aeronautics and Space Administration’s Goddard Space Flight Center in Greenbelt, Md. “One of our top goals is to see how stars grow with their young planets.”

Astronomers will also use the new telescope to probe black holes at the centers of galaxies, search for the chemical signatures of life on extrasolar planets and, closer to home, study the frozen oceans on moons at the edge of our own solar system.

The $10 billion, truck-size telescope, now nestled inside the nose cone of a rocket, is poised for launch from Europe’s Spaceport along the Atlantic coast in French Guiana. Once it clears Earth’s atmosphere, it will set course on a 29-day voyage to a spot four times as far away as the moon. Plans call for the spacecraft to orbit the sun at this spot, called the second Lagrange point, at least through 2026, collecting distant starlight with its huge, gold-coated mirror and beaming back a steady stream of images and data.

The Webb’s ultrasensitive infrared sensors are designed to capture light emitted more than 13.6 billion years ago by primordial stars, gargantuan furnaces that were hundreds of times larger than any stars shining today. It could reveal the earliest star clusters and supernovas, where almost all the elements were forged.

JAMES WEBB SPACE TELESCOPE

The Webb mirror has 6.25 times as much collecting area as the Hubble’s.

JAMES WEBB SPACE TELESCOPE

The Webb mirror has 6.25 times as much collecting area as the Hubble’s.

JAMES WEBB SPACE TELESCOPE

The Webb mirror has 6.25 times as much collecting area as the Hubble’s.

“We want to see the first objects that formed as the universe cooled down after the Big Bang,” Dr. Mather said. “We don’t know exactly when the universe made the first stars and galaxies, or how for that matter. One way or another, the first stars must have influenced our own history, beginning with stirring up everything and producing the other chemical elements besides hydrogen and helium.”

Stretched by time and distance, that first starlight has shifted from visible or ultraviolet light into redder wavelengths that are invisible to the Hubble Space Telescope and most terrestrial telescopes, because moisture in the atmosphere strongly absorbs infrared radiation.

By looking in the infrared, the Webb telescope also will be able to see through the cosmic dust that ordinarily obscures exoplanets, which are those outside our solar system orbiting other stars, and galaxies.

“The Webb will be able to see in the infrared stars and galaxies that were a hundred times fainter than was previously possible,” said Klaus Pontoppidan, a project scientist at the Space Telescope Science Institute in Baltimore, which will manage the telescope once it is in space.

The Webb also carries an advanced chemical analyzer called the Near Infrared Spectrograph that collects data about variations in light to reveal the temperatures, masses and chemical compositions of stars and planets.

“We will be able to take a hundred spectra or more at the same time in a single exposure,” said Antonella Nota, a Webb project scientist with the European Space Agency. “Images are worth a thousand words; spectra, for astronomers, are worth a thousand images.”

In the telescope’s first year of operation, astronomers plan to use it to analyze atmospheres of 65 planets that orbit stars light-years away from our own solar system, seeking evidence of water, carbon dioxide, methane and ammonia. “We will be able to look in the atmospheres of the planets to identify elements that are signs of life as we know it,” said Begoña Vila, an instrument systems engineer for the telescope.

Unlike the Hubble telescope, which orbits the Earth, the Webb will travel around the sun.

Hubble orbit

350 miles

from Earth

Hubble orbit

350 miles

from Earth

Hubble orbit

350 miles

from Earth

The Webb mission gets under way at a critical time for astronomy, as light pollution—including that caused by vast networks of satellites now being sent into Earth orbit—is making it hard to study the stars from our planet’s surface.

“Even at the North Pole there will be light pollution from satellites,” said Samantha Lawler, an astronomer at Campion College and the University of Regina in Saskatchewan, Canada, and the lead author of a study on light pollution to be published in the Astronomical Journal. So many brightly shining satellites girdling Earth “will have a devastating effect on astronomy and stargazing world-wide.”

From deep space, however, the view is still unobstructed.

Ten years late and 10 times over budget—in large part because of a series of design, production and quality-control lapses that a NASA review board laid at the feet of prime contractor Northrop Grumman Corp. and others—the Webb telescope is among the most expensive science instruments ever built. Engineers had to fix faulty welds, missing bolts and tears in the telescope’s giant sunshield, among other problems.

“The complexity of this first-ever program inevitably creates opportunities for human error in design, manufacturing, integration and testing,”

Wesley Bush,

then the chief executive officer of Northrop Grumman, said in testimony to the House Committee on Science, Space and Technology in 2018. “And we have experienced some errors.”

If all goes planned, the Webb telescope will join more than two dozen telescopes already in space, ranging from the vintage $11.3 billion Hubble telescope to the $188 million X-ray Polarimetry Observatory, which launched earlier this month to study pulsars, neutron stars and black holes.

But NASA scientists are acutely aware of the risks involved in sending such a complicated instrument into such a hostile environment—especially since the Webb telescope will be too far away for any repair missions of the sort that NASA mounted to correct problems with the Hubble telescope.

The Webb telescope’s gold-plated main mirror, measuring 21 feet in diameter, is too big to fit inside the nose cone of any existing rocket. So NASA engineers built it in 18 segments that fold up like the petals of an origami flower. They packed these and other parts of the telescope inside the European Ariane-5 rocket—including solar panels and a tennis-court-size sun screen designed to keep the instrument at its minus 390 degree Fahrenheit operating temperature.

Once in space, the mirror will take 10 days or so to unfold. NASA calls this remote-control effort one of the most complicated operations ever attempted in space. Like an elaborate Rube Goldberg contraption, it will take 50 mechanical procedures involving 70 hinges, 90 cables, 140 releases and 400 pulleys, NASA officials said.

For the 18 mirror elements to function as a single, perfectly focused lens, telescope engineers said, each must be aligned by remote control to within a fraction of a wavelength of near-infrared light—about 1/10,000 the thickness of a human hair. To fine-tune them, 126 actuators will bend or flex each mirror into a specific prescription, a process that will likely take months.

“We will rebuild it in orbit,” Mike Menzel, lead systems engineer for the Webb at NASA’s Goddard Space Flight Center, said of the mirror. ”This has never been done before.”

All told, it will take about six months of setup and calibration before the telescope is ready to start scientific observations.

“I won’t breathe a sigh of relief until 180 days after launch, when we are operational,” said Bill Ochs, NASA Webb project manager.

Write to Robert Lee Hotz at sciencejournal@wsj.com