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It finally happened. After decades of planning, budgeting and testing, the most powerful space telescope ever launched on December 25th 2021. It's a joint mission between NASA, the European Space Agency, and the Canadian Space Agency called the James Webb Space Telescope.

And it has the power to help us understand everything from our solar system to the earliest days of the universe. Just, not yet.

Webb might have launched in December, but the first images aren't expected until at least June, and that's because the launch was only the beginning.

Here's what needs to happen before we can start  learning the secrets of the cosmos. Ultimately, the reason  Webb needs six months after launch to become e fully operational is because of how complex its mission is.

The telescope will observe and analyze everything from planets to stars to the first galaxies and it's mainly going to do that by collecting infrared light.

Unlike visible or ultraviolet light, infrared doesn't really get scattered or absorbed by dust in space. The light wavers are wide enough that they can weave right around dust particles, so they can travel much farther.

That means collecting infrared light will  allow Webb to observe especially faraway objects. The telescope will also be able to study things like old stars and planets glow more brightly in infrared than in visible light. It will even  be able to pick up light from the very earliest galaxies.

So, you can see why there was so much hype around this telescope. That said, building a powerful infrared telescope comes with major challenges. For one, Webb needed a giant mirror. Telescope mirrors collect light and ultimately focus it onto a detector. and if you're trying to collect light from some of the faintest most distant objects out there, you're going to need a lot of mirror.

Though Webb isn't the first infrared telescope, it is the biggest. Its primary mirror is about six and a half metres across, almost twice as wide as the previous record holder, the European Space Agency's Herschel telescope. And while that will allow Webb to make really high-resoltion observations, it also meant that the telescope was too big to fit on top of any rocket. Even the beefy Ariane 5 provided by the European Space Agency. That's part of why it's taking six months to get this thing live.

To get it in a rocket, engineers had to design Webb to fold up. Then, after launch, the telescope had to spend a few weeks slowly unfolding, like the world's most expensive origami project. No other telescope has had to do this. But thanks to those years of design and testing, all 50 major deployments worked. Webb unfolded its solar array, which collects sunlight to power the telescope, as well as an antenna, the secondary mirror, and more. 

In mid January, it also unfolded the two wings of its mirror. So, now all the major parts of the space craft are in the right configuration. Along the way, Webb also unfolded its sun shield, which is about the size of a tennis court. It's made of five sheets of material coated with aluminium and it's critical for Webb's missions because that's the second hard thing about building an infrared telescope. The main source of infrared light is heat and even something like the moon gives off enough heat that it would drown out the faint signals Webb is looking for. So, the telescope has to be incredibly cold and by blocking infrared light from the sun, the moon and the Earth, the sun shield is a key part of it.

Now, by the time you watch this, Webb should have reached its final orbit, around a point called L2 or the second Legrange point. If you drew a line from the sun to the Earth, then kept going another 1.5 million kms, that's L2. And it's a gravitational fixed point that never moves relative to Earth, so it's always right in line with us. But if engineers parked Webb right in L2, Earth would block a good amount of the sun light powering the space craft, and radio emissions from the Sun would interfere with communication. So, by orbiting this point instead, Webb avoids those problems, but keeps one of L2's big perks. From Webb's perspective, the Earth and the Sun will be in the same part of the sky, so it will be easier for Webb to block their heat with its sun shield. But even now, it's still not time to start observations. After its journey, the telescope needs to chill, literally. Hiding behind its sunshield, it will taker roughly a month for most of the telescope to reach its operating temperature: a balmy -233°C, and then the spacecraft will need to be thoroughly tested and calibrated. Engineers will need to make sure the instruments work, and that all 18 segments of the mirror are perfectly aligned to within a few nanometers. That way, the individual panels will be able to work together as one giant mirror. Then, at long last, the day will come. The team will give the command, and the James Webb Space Telescope will start collecting data for scientists around the world. And the whole SciShow team will probably be crying tears of joy. But for now, we'll have to wait. Really, it's not a surprise that engineers want to get this right. They spent decades and billions of dollars on this project. And it's arguably the most ambitious scientific project ever launched, and soon, it could get us closer to answering some of the biggest questions we have about the universe. But for now, we'll have to be patient a little longer.

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