The countdown has begun. The mighty James Webb Space telescope will launch next month. It is the start of a mission that could have far-reaching implications for our understanding of the cosmos.

We had to wait a long time for it. But on December 24, the time has finally come. The James Webb Space Telescope (JWST for short), propelled by an Ariane 5 rocket, will take to the skies and set course for Lagrange Point 2. From there, the most powerful space telescope ever built should make countless discoveries.

What exactly is the James Webb Space Telescope?

The James Webb Space Telescope is a huge infrared telescope built by the US Space Agency in conjunction with the European and Canadian Space Agency. The telescope is about the size of a tennis court and as heavy as a school bus. The most eye-catching part are the 18 small mirrors that, once in space, have to serve as one huge (6.5 meters wide) mirror. The telescope is so large that it actually does not fit in the nose of an Ariane 5 rocket. But researchers have found something on that. The telescope is ingeniously folded and unfolded once in space. The telescope is expected to take about two weeks to unfold. But then you have something; once operational, James Webb will be the most powerful space telescope ever built.

The huge mirror of the James Webb Space Telescope. Image: NASA/Desiree Stover.

What will the James Webb Space Telescope be investigating?

Are we alone? It is a question that has haunted people for centuries. And we finally have the technology to answer that. The James Webb Space Telescope (JWST for short) can also be counted among them. The telescope was designed, among other things, to investigate the atmospheres of planets outside our solar system and to look for traces of life in them (see box).

If you were a curious alien to look at the atmosphere of our planet from a distance, you would probably quickly come to the conclusion that the Earth is home to life. Our atmosphere is very oxygen-rich. And that’s special. Because originally the Earth’s atmosphere did not contain much oxygen at all. That only changed when cyanobacteria arose about three billion years ago and started producing oxygen through photosynthesis. And so the oxygen in the Earth’s atmosphere testifies to the presence of life. In addition to these so-called biosignatures, there are also other indications of life in the atmosphere. Such as, for example, the high concentration of greenhouse gases that we have pumped into it ourselves. In a similar way, we can also look for traces of life in the atmospheres of other planets. And James Webb is perfect for that.

But the JWST isn’t just looking for life. The powerful telescope should also be able to detect the first galaxies that formed shortly after the Big Bang and thus provide more insight into the evolution of the universe. In addition, the telescope will also investigate the formation of stars and planets, open the hunt for Earth-like planets and shed new light on the evolution of galaxies.

Can we expect spectacular images?

We’re pretty spoiled by the forerunner of the James Webb Space Telescope: Hubble Space Telescope. This mainly optical telescope has delivered countless spectacular images in recent decades. And it naturally raises the question of whether the infrared James Webb Space Telescope can match that. The answer is: yes! In fact; scientists expect James Webb’s images to be even more detailed and spectacular than Hubble’s. So that’s promising.

Hubble is an optical telescope, but it can also observe at infrared wavelengths. This photo, made by Hubble, shows that the latter can also produce beautiful images. Here we see the Horsehead Nebula in infrared. Now consider that the James Webb Space Telescope is much more powerful than Hubble and is also designed to observe in infrared (but can also see some optical light). Then it becomes clear that we can expect much nicer images from this telescope. Incidentally, Hubble didn’t deliver this photo of the Horsehead Nebula like that; all Hubble images are black and white and are colored on Earth. The result does not always correspond to what you would see if you traveled to the respective space phenomenon; the objects are regularly colored in such a way that interesting properties are highlighted. In a similar way, the infrared data provided by James Webb will soon be translated by computers into a breathtaking and informative picture. Image: NASA/ESA/the Hubble Heritage Team (STSci/AURA).

Why does the James Webb Space Telescope study the universe in infrared?

As mentioned, James Webb will hunt for the first galaxies. To do this, the telescope has to peer deep into space. The following applies: the deeper the telescope peers into space, the deeper it also looks into history. But at the same time, the universe is also expanding. This also means that the deeper we look into the universe, the faster objects move away from us. And those objects have a greater redshift. That means the ultraviolet or visible light they give off shifts toward the infrared. In order to observe the first galaxies, the telescope must therefore observe this young universe in infrared light. This is also necessary when investigating the formation of stars and planets much closer to home. They are usually hidden in dust. And an infrared telescope can see right through it.

How long will the James Webb Space Telescope be active?

The telescope will have to conduct research for at least five years. However, the mission can then be extended for another five years.

Setback
The idea that a powerful space telescope could follow Hubble originated in the 1990s. The telescope was supposed to take to the skies sometime in 2007. Construction of the telescope started in 2004. But it soon became clear that it was not so easy to turn the construction drawings into reality. Setback after setback followed and the launch date was repeatedly pushed forward and the budget was repeatedly stretched. Reason enough for a committee of the US House of Representatives to propose in 2011 that the entire mission be called off. But astronomers vehemently opposed that plan and the telescope was saved. In the years that followed, however, the launch was pushed further and further and the budget stretched further. If the telescope goes into the sky next week, there will be a delay of about 14 years. And with a budget of 8.8 billion US dollars, the telescope is also about 17 times more expensive than budgeted in the 1990s.

When can we expect the first images?

Our patience will be tested again after the launch of the James Webb Space Telescope. For example, it takes about a month for the telescope to settle in Lagrange point 2. During that period, the telescope not only travels to Lagrange point 2, but it also unfolds completely. And that is an exciting period, because nothing can go wrong.

Once it has arrived at its destination, the telescope must first cool down in order to use its near-infrared camera without noise. Once that camera is operational, the 18 mirrors can be aligned so that they function as one mirror. That all takes quite some time; The James Webb Space Telescope is expected to be fully operational about six months after launch. The first images are expected shortly before that.

In order to launch the huge telescope, it must be folded. Image: Northrop Grumman.

What will the James Webb Space Telescope look at first?

It is the dream of many astronomers to work with the data collected by this telescope. This became apparent when the concerned space agencies announced that researchers could submit plans for James Webb’s first 6,000-hour observation run. More than 1,100 proposals were received from scientists from 44 different countries. Some of those proposals have been accepted. For example, astronauts will use the telescope to investigate the atmosphere of the Earth-like exoplanet GI486b, to find out whether lava is raining on the exoplanet 55 Cancri e and to find out whether Trappist-1c has an atmosphere. Even closer to home, there are still plenty of unanswered research questions. For example, the telescope will also investigate the moons of Uranus, the climate of Pluto and comet Hale-Bopp. A complete overview of all accepted proposals is here to find.

Astronomers eagerly await the launch of the James Webb Space Telescope. The telescope is expected to answer many questions and radically change our view of the universe and its creation. But not only that; in the hunt for extraterrestrial life, the telescope could also forever change the way we view our own planet and ourselves. Because is the earth with its habitable conditions really so special? And is the fact that numerous species have arisen here so unique? Or does it happen on other planets or moons as well? Finally, the James Webb Space Telescope will undoubtedly also raise new research questions. And perhaps the telescope will even encounter phenomena that we cannot yet imagine. All in all, it seems almost self-evident that in ten years’ time we will come to the conclusion that the mighty James Webb Space Telescope was well worth the long wait and almost infinite stretching of the budgets.