Successful take-off of the Webb telescope – ushering in a new era in astronomy

The James Webb Space Telescope – humanity’s biggest bet to date in its quest to probe the Universe – flew into space on December 25, marking the culmination of decades of work by the world’s astronomers whole. But for Webb to begin a new era in astronomy, as many scientists hope, hundreds of complex engineering steps will need to go off without a hitch in the days and weeks to come.

“Now the hard part begins,” says John Grunsfeld, astrophysicist and former astronaut and scientific director of NASA.

The $ 10 billion Webb is the most complicated and expensive space observatory in history, and the successor to NASA’s Hubble Space Telescope, which has studied the Universe since 1990. Afterwards Its launch, Webb will now embark on the riskiest part of his mission – deploying all the parts necessary for his enormous mirror to peer deep into the cosmos, towards the dawn of time.

It is only when all the equipment is working and the first scientific observations have been made, probably in July, that astronomers will be able to relax. By then, “it’s going to be a lot of nervousness,” says Heidi Hammel, interdisciplinary scientist for Webb and vice president for science at the Association of Universities for Astronomical Research in Washington DC.

The NASA-built Webb was launched at 9:20 a.m. local time from the Kourou spaceport in French Guiana, on an Ariane 5 rocket provided by the European Space Agency (ESA). The third international partner of the project is the Canadian Space Agency.

“What an emotional day,” said Thomas Zurbuchen, NASA scientific director, on a webcast from the launch site. “This is the start of one of the most amazing missions mankind has designed.”

“I feel very moved right now after seeing something that we have all been waiting for so long to finally happen,” adds Jeyhan Kartaltepe, an astronomer at the Rochester Institute of Technology in New York who received observation time on Webb. “I am very grateful to everyone who worked so hard to make this a success.”

Telescope images: NASA

Set a course

The Ariane 5 carried Webb on a seemingly flawless path through space, saving more fuel for the telescope to use for science in years to come. After separating from the launcher 27 minutes after launch, Webb deployed his solar panels, a crucial step that allowed electrical energy to start flowing. “It was half an hour on the edge of my seat,” says Grunsfeld. A few hours later it was expected to burn its engines to get it going to its final destination, a position in space known as the second Lagrange point, or L2 (see “Voyage de Webb ”). There, 1.5 million kilometers from Earth, it will always be on the opposite side of the planet to the Sun, gazing into the dark regions of space with its sensitive optics sheltered from sunlight.

The journey to L2 will take 29 days, with over 300 “points of failure” at which something could go wrong. The whole process is like a butterfly emerging from its chrysalis, says Günther Hasinger, ESA Scientific Director, a very expensive and very complex three-story butterfly.

The first and most crucial is the deployment of Webb’s kite-shaped sunshade, which is the size of a tennis court. The shield’s job is to protect Webb from radiation and cool the environment from 110 ºC on the sunny side to -235 ºC on the shaded side. Webb needs freezing temperatures so that his optics can pick up glows from distant galaxies and other cosmic objects in infrared wavelengths.

The Ariane 5 rocket with NASA's James Webb Space Telescope on board, on the launch pad.

The telescope launched on a European Ariane 5 rocket.Credit: Bill Ingalls / NASA

“The unique thing about Webb is that it’s a cold telescope,” Hasinger explains. If the sunshade does not deploy properly, Webb’s science will be severely degraded.

Three days after the launch, two rectangular pallets are supposed to be deployed on either side of the observatory. Over the course of an additional four days, the pallets will open to reveal the five membrane-shaped layers of the sunshade, then stretch them out and secure them in place, like tightening a sheet over a mattress.

Mirror alignment

Ten days after launch, if all goes well, Webb will move his small secondary mirror to face his giant primary mirror, which will still be folded up. Two days later, the main mirror will begin to set up two hinged sections to create the full 6.5 meter wide mirror. At this point, the mirror’s 18 hexagonal segments, made of beryllium and coated in gold, will look like a gigantic glittering honeycomb – and Webb will become a real telescope, says Hammel, because he will be able to capture light.

Roughly two weeks later, Webb is expected to reach his final location at L2. It’s too far from Earth for astronauts to visit and repair the telescope if something goes wrong, as they did after Hubble launched with faulty optics. (Astronauts, including Grunsfeld, ultimately made it to Hubble five times to upgrade its science instruments and keep it as a world-class observatory.) But if the lens hood and mirrors deploy properly, the worst is behind Webb. . It is therefore a matter of aligning the mirrors and calibrating the instruments. These steps are complicated but have already been performed on telescope mirrors on the ground.

One of the reasons it will be six months before science can begin is because the telescope needs time to cool down to its operating temperature. Only about four months after launch, the segments of the primary mirror will be sufficiently cooled and aligned to assume the correct shape. Mission engineers will then begin to calibrate the instruments.

And one of the telescope’s four instruments, which will operate at mid-infrared wavelengths, requires another cooler to reach -266 ºC, just 7 ºC above absolute zero. Once this temperature is reached, Webb should be 100 times more sensitive than Hubble.

NASA's James Webb Space Telescope with its 5-layer sunshades open for deployment testing.

The telescope’s beryllium and gold mirror sits in the middle of a five-layer lens hood.Credit: Chris Gunn / NASA

Infrared eyes

Webb’s infrared vision will allow him to scan more than 13.5 billion years back, towards distant stars and galaxies whose light has been extended to infrared wavelengths by the expansion of the Universe. It will also be able to penetrate dust-covered regions such as the birthplaces of stars, and probe the atmospheres of planets beyond the solar system. “It is designed to answer outstanding questions in all areas of astrophysics,” says astronomer Antonella Nota, ESA’s project scientist for Webb.

If all goes as planned over the next six months, scientists on the mission will be under intense pressure to release stunning images and data from Webb as soon as possible. A small committee of astronomers from the Space Telescope Science Institute in Baltimore, Md., Which operates Webb, has compiled a secret list of objects to observe first. The first slice of results will likely include spectacular images and data of planets, stars and galaxies, to show the telescope’s capabilities. After that, the science will start in earnest for the other astronomers lining up to use Webb.

For now, they can only watch and wait to see if the telescope performs as its designers expect. “I know we did all we could,” says Hammel.


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