Astronomers are beginning to breathe once more.

Two weeks in the past, essentially the most highly effective house observatory ever constructed roared into the sky, carrying the hopes and desires of a era of astronomers in a tightly wrapped package deal of mirrors, wires, motors, cables, latches and willowy sheets of skinny plastic on a pillar of smoke and hearth.

On Saturday, the observatory, the James Webb Space Telescope, accomplished a last, essential step round 10:30 a.m. by unfolding the final part of its golden, hexagonal mirrors. Nearly three hours later, engineers despatched instructions to latch these mirrors into place, a step that amounted to it changing into totally deployed, in keeping with NASA.

It was the latest of a sequence of delicate maneuvers with what the house company referred to as 344 “single points of failure” whereas rushing distant in house. Now the telescope is nearly prepared for enterprise, though extra tense moments are nonetheless in its future.

“I’m emotional about it,” Thomas Zurbuchen, NASA’s science chief, mentioned of all of the telescope’s mirrors lastly clicking into place. “What an amazing milestone — we see that beautiful pattern out there in the sky now almost complete.”

The James Webb Space Telescope, named after a former NASA administrator who oversaw the youth of the Apollo program, is 25 years and $10 billion in the making. It is thrice the dimensions of the Hubble Space Telescope and designed to see additional into the previous than its celebrated predecessor in order to review the primary stars and galaxies to activate in the daybreak of time.

The launch on an Ariane rocket on the morning of Dec. 25 was flawless; so flawless that the engineers mentioned it saved sufficient maneuvering gasoline to increase the mission’s estimated 10-year lifetime, maybe by as a lot as a further 10 years, mentioned Mike Menzel, a mission methods engineer at NASA Goddard. But the telescope should full a monthlong journey to a spot 1,000,000 miles up, far past the moon’s orbit, referred to as L2, the place gravitational fields of the Earth and solar commingle to supply the circumstances for a steady orbit across the solar.

With a main mirror 21 ft throughout, the Webb was too massive to suit in a rocket, and so the mirror was made in segments, 18 gold-plated hexagons folded collectively, that must pop into place as soon as the telescope was in house.

Another problem was that the telescope’s devices needed to be delicate to infrared or “heat radiation,” a type of electromagnetic radiation invisible to the human eye. Because of the growth of the universe, essentially the most distant and earliest galaxies are flying away from us so quick that seen gentle from these galaxies shifts into the longer infrared wavelengths. As a outcome, the Webb will view the universe in colours no human eye has ever seen.

But in order to detect infrared radiation from distant sources, the telescope must be very chilly, just a few levels above absolute zero, in order that the telescope itself doesn’t intrude with the work.

After years of deployment assessments on Earth, small surprises in house have popped up throughout the Webb’s deployment, or the “getting-to-know-you phase of the telescope,” Bill Ochs, an engineer on the Goddard Space Flight Center and a challenge supervisor for the telescope, informed reporters on Monday.

Mission managers detected excessive temperatures on an onboard motor used solely in the deployment course of, so engineers repointed the telescope on Sunday to guard the system from the solar’s warmth. Then the Webb’s photo voltaic arrays have been readjusted when engineers observed the telescope had smaller energy reserves than anticipated.

One of essentially the most dicey moments got here on Tuesday, with the profitable unfolding of an enormous sunscreen, the dimensions of tennis courtroom. It was designed to maintain the telescope in the darkish and chilly sufficient in order that its personal warmth wouldn’t obscure the warmth detected from distant stars. The display is made of 5 layers of a plastic referred to as Kapton, which has similarities to Mylar and simply as flimsy, and which had often ripped throughout rehearsals of its deployment.

In reality, the unfolding went flawlessly this time.

“It went incredibly smoothly. I feel like we’ve all kind of been shocked that there’s been no drama,” mentioned Hillary Stock, a sunshield deployment specialist at Northrop Grumman, the telescope’s main contractor.

Then on Wednesday, the telescope unfurled its secondary mirror, which factors on the 18 hexagons, reflecting what the telescope noticed again to its sensors.

“We’re about 600,000 miles from Earth, and we actually have a telescope,” Mr. Ochs mentioned in the mission operations management room on the Space Telescope Science Institute in Baltimore.

As the telescope ticked off one chore after one other, the astronomers who had been ready 25 years for this telescope started to loosen up.

“Strangely I don’t feel so anxious anymore, my inherent optimism (hello optimism bias & anchoring bias) is in full gear,” Priyamvada Natarajan, a cosmologist from Yale, wrote in an e-mail.

Three days later the final mirrors locked in place, and the staff at mission management broke into applause and a flurry of excessive fives and fist bumps.

“How does it feel to make history everybody?” Dr. Zurbuchen requested the mission’s managers in Baltimore after the latching was full. “You just did it.”

“NASA is a place where the impossible becomes possible,” mentioned Bill Nelson, the previous senator and astronaut who’s now NASA’s administrator.

Garth Illingworth of the University of California, Santa Cruz, mentioned: “I cannot describe how incredible this feels to have a full mirror. It is an astonishing achievement for the J.W.S.T. Team.”

Alan Dressler of the Carnegie Observatories, who chaired a report that led to what would change into the Webb telescope, mentioned “what resonates at this moment is the extraordinary ability of our species to collaborate, to organize thousands of people to work carefully, relentlessly, unselfishly, and seemingly endlessly toward some greater human good.”

Chanda Prescod Weinstein, an astrophysicist on the University of New Hampshire, echoed his remarks: “This is such a reminder of how successful people can be when they work together.”

While the telescope is taken into account totally deployed, a lot stays to be accomplished. There are nonetheless 49 of these “single point failures,” in keeping with Mr. Menzel. Problems with any of them might have an effect on the mission’s particular person devices or the whole spacecraft.

By the tip of January, the telescope will probably be in its last orbit at L2. The astronomers will spend the following 5 months tweaking the mirrors to carry them into widespread focus and starting to check and calibrate their devices.

Then actual science will start. Astronomers have mentioned the primary image from the Webb telescope will seem in June, however of what no person will say.

Jane Rigby, a challenge scientist for the mission at NASA Goddard, mentioned in a information convention on Saturday that the primary photos made throughout the mirror alignments will probably be blurry and ugly. But as soon as the mirrors are coaxed into working collectively, she mentioned photos from the telescope would “knock everyone’s socks off.”

“We are planning a series of ‘wow’ images to be released at the end of commissioning when we start normal science operations that are designed to showcase what this telescope can do,” Dr. Rigby mentioned.

“I can’t wait for first light and then first science,” Michael Turner, a veteran cosmologist on the Kavli Foundation in Los Angeles, wrote in an e-mail. “It will be even better for our COVID-riddled spirits than Ted Lasso.”