The ??? ??? ??? ??? ??most powerful telescope ever rocketed into space arrived at its destination Monday, concluding a white-knuckled journey from its launchpad in South America to a sweet spot in orbit about 1 million miles away.

In the first days following the James Webb Space Telescope’s liftoff on Dec. 25, the spacecraft blew past its low Earth-orbiting predecessor, the Hubble Space Telescope, and put the moon in rearview. During a month of traveling since Christmas, the spacecraft completely unfolded its antennas, tennis-court-sized sunshield, and mirrors like a Swiss Army knife. On Monday, the mission's ground team fired Webb’s thrusters to nudge the observatory to its final post in an orbit around the sun. NASA announced it arrived at 2:24 p.m. ET.

The achievement marks the completion of a series of complicated, first-of-its-kind maneuvers in space and a crucial make-or-break period for the $10 billion telescope that some experts forewarned as "30 days of terror." But with diligent planning and careful rocket engineering, the terror never came to pass.

"You've heard people talking about how it looked so easy. It is not easy. NASA makes it look easy, and sometimes they’re a victim of their own success," Heidi Hammel, a planetary astronomer and part of the Webb telescope's science team, said during a phone briefing with reporters. "We all, as humanity, can be proud that we are working collectively to do great things, to expand our knowledge of the universe, to make the universe more accessible to all of us."

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Webb, with its giant infrared telescope, will observe some of the oldest, faintest light in the universe. It will study a period less than 300 million years after the Big Bang, when many of the first stars and galaxies were born. Scientists also will use the powerful telescope to peer into the atmospheres of planets outside our solar system, called exoplanets. Findings of water and methane, for example, could be potential hints of habitability or biological activity, i.e., life.

Astronomers anticipate the telescope will facilitate a golden age in our understanding of the cosmos, with 10 to 20 years of never-before-seen snapshots of space billions of light-years away.

The massive telescope has perched in a place dubbed "L2," or the second Lagrange point. The location is named after Joseph-Louis Lagrange, an 18th-century mathematician who solved the "three-body problem." The question was if a configuration existed in which three masses could orbit each other and stay in the same position relative to each other. It turns out there are five such points where that can happen, and the second is where Webb will conduct unprecedented science.

L2 is an ideal vantage point because it will keep the radiant sun and Earth at the observatory’s back, facing away from our star to get clear views of deep space. From this location, Webb will move in unison with Earth so its robust sunshield can constantly block the sun, moon, and Earth’s light and heat.

The -388-degree Fahrenheit temperature at L2 makes it possible for Webb to see distant stars and galaxies in infrared, an invisible light commonly understood (or felt) as heat radiation. To detect dim objects, the telescope needs to be extremely cold to pick up faint heat signals from trillions of miles away.

At L2, Webb will also be close enough to Earth to regularly communicate through the Deep Space Network, an international array of jumbo antennas supporting NASA’s deep space missions. And, critically, the side of the spacecraft facing the sun will have constant access to solar power.

Before Monday's maneuver, NASA exuded confidence. The team had already implemented vital rocket thrusts to tweak the spacecraft's trajectory, said Mike Menzel, Webb’s mission systems engineer. The final thrusts helped avoid overshooting the L2 mark. That's crucial. There's no option to turn around and propel back towards Earth, explained Randy Kimble, a Webb commissioning project scientist, in a blog post. Doing so would expose the telescope’s optics to the sun, overheating and ruining the instruments.

The last thrust gave Webb just enough of a boost to "insert" into its orbital position. "We're not at all worried about it," Menzel had said earlier this month. "It’s a very minor burn."

The near-perfect execution of the mission so far has been a welcome surprise to mission planners. When it comes to space missions, their modus operandi has been to expect the unexpected. The initial troubles with Hubble — NASA had to send astronauts out to the observatory to fix the blurry telescope in 1993 — perhaps also put Webb's team on edge. If problems arose this time, Webb would be too far from home to send repair workers.

Webb, a collaboration between NASA, the European Space Agency, and the Canadian Space Agency, is now preparing for science operations. The next step will involve the careful calibration of the telescope’s 18 hexagonal mirrors pieced together in a massive honeycomb dish. All of the segments must work in harmony to take uniform images of deep space. The first crisp pictures ready for primetime will be released in June.

"The core science of this telescope was to see the very first light in the universe, the first galaxies that formed, with some clever projects, perhaps even the first stars that formed," Hammel said. "That's its raison d'être. That's why it was built the way it was built."