James Webb: 13 Questions to Understand the Space Telescope Mission

The James Webb Space Telescope (JWST) is in place 1.5 million kilometers from Earth. In mid-July 2022, the very first official images of the observatory were released. The result is fabulous. Hubble’s legacy is secured.

James Webb has finally shown what he is capable of. The space telescope, which is now located 1.5 million kilometers from Earth, got a first historic photo of the bottom of the universe, released on July 11, 2022. The event was so historic that even Joe Biden, the president of the United States, joined the celebrations. Even in France, Emmanuel Macron went there with his tweet.

Then on July 12, the observatory delighted astronomers, the public and journalists even more with snapshots that showed the remains of a dying star, a cosmic ballet between four galaxies, the secrets of a giant exoplanet and what look like cosmic rocks – where stars are born, in big fogs. These photos of James Webb are stunning.

The capabilities of the telescope, developed by the US Space Agency with the help of its European and Canadian counterparts, are colossal. Just do a simple comparison between James Webb and Hubble. Or to see how the area photographed by the observatory is only a small fraction of the entire universe. And yet the details are incredibly accurate.

Here’s everything you need to know about the very exciting JWST mission, which will be able to deliver spectacular observations of space to astronomers around the world.

What about the James Webb Telescope?

It’s done: The James Webb Telescope is in space! The launch was successful on December 25, 2021. After that, it was left to make it fully operational. In total, more than 300 critical points have been identified as potentially problematic during implementation; apparently they were closely scrutinized by NASA.


What is the James Webb Telescope used for?

This observatory is designed to promote research in four main areas:

  • Discover the light from the first galaxieswhich appeared shortly after the Big Bang,
  • To study the formation and evolution of galaxies,
  • Better understand the birth of the stars,
  • As well as exoplanets.

For this, JWST observes in the infrared range (that is, the radiation between visible light and microwaves) and in space. The observatory is thus able to go far back into the universe’s past, to see the first galaxies in formation – “baby galaxies” – and to inspect the interior of the dust clouds in which stars and planets formed.

What are the instruments of the James Webb Telescope?

The observatory has four scientific instruments on board:

  • ONE near infrared cameraNIRCam (for “Near-InfraRed Camera”), which will, among other things, detect stars that appeared after the Big Bang, search for supernovae, measure distorted light due to dark matter,
  • ONE near infrared spectrometerNIRSpec (“Near-Infrared Spectrometer”), which makes it possible, for example, to study the chemical elements in distant galaxies or clusters of young stars,
  • ONE mid-infrared instrumentMIRI (“Mid Infrared Instrument”), with which it is especially possible to observe brown dwarfs, exoplanets and the evolution of stars and protoplanetary systems,
  • And one near infrared imaging camera and slitless spectrographsays NIRISS (“Near Infrared Imager and Slitless Spectrograph”), which helps study exoplanets and distant galaxies.

Why does the James Webb Telescope have a segmented mirror?

The James Webb Telescope’s sumptuous primary mirror, with an estimated diameter of 6.5 meters, does not go unnoticed with its golden color and 18 segments arranged in a hexagonal shape. In astronomy, the mirror is said to be segmented. It is not a technical choice, because it would have been possible to build it in a single block.

There is a logistical motivation behind this choice: it would have been impossible to mount a mirror of this size consisting of a single block in the rocket that sent JWST into space. For the first time, it was therefore decided to launch a telescope with a segmented mirror into space.

Will the James Webb Telescope replace Hubble?

It would not be entirely correct to say that the James Webb Space Telescope is intended to replace Hubble. You should see him more as a successor. Admittedly, JWST exceeds a limit for Hubble, which turns out to be unable to see beyond the near-infrared (it therefore goes back less far into the past than JWST does). It is also larger than Hubble in size.

But the day Hubble no longer works, the James Webb Telescope will not have the means to completely replace it. Currently, Hubble is the only telescope capable of observing in ultraviolet light, and JWST is not equipped to do the same.

When was the James Webb Telescope launched?

The James Webb Space Telescope was originally scheduled to launch on December 18, 2021. In the end, its launch took place on Christmas Day, December 25, 2021.

Where was the James Webb Telescope launched from?

It took off from the Kourou Space Center in French Guiana, carried aboard an Ariane 5 ECA rocket. The observatory had to be transported by boat from California to reach its launch base.

How much does the James Webb Telescope cost?

The total cost of the telescope is estimated at 9.7 billion dollars, or 8.2 billion euros. Since the start of the project, this budget has been continuously revised upwards.

NASA mentions that it participates in the total cost of JWST to the value of 7.998 billion dollars. She estimates that the first five years of operation of the observatory, added to the two years needed to exploit its data, will generate an additional cost of $8.835 billion – knowing that JWST should surely double its lifetime.

Why has the launch of the James Webb telescope been delayed?

JWST’s flight into space has been repeatedly postponed. In 2003, the planned date for its departure into space was 2011. Nevertheless, the schedule had to be adjusted that year due to regular problems and the increase in the budget. Representatives of the US Congress have even considered canceling the project, which has become too expensive. However, the launch was pushed back to 2018.

And since then, take-off has continuously been postponed. The Covid-19 pandemic has further disrupted the pace of work and forced the launch date into space to be further postponed to the end of 2021.

Why is the name of the James Webb Telescope controversial?

At the start of the project, the telescope was given the temporary designation “Next Generation Space Telescope” (NGST, for “Next Generation Space Telescope”). It was so named to symbolize the continuity of its activities compared to Hubble’s.

JWST received its official name on September 10, 2002, in reference to James Webb (1906–1992), NASA’s second administrator. He is known for leading Apollo. Nevertheless, this choice of name is questioned by many and many scientists because James Webb would have advocated a policy of exclusion of LGBTQI+ people within the space agency. However, NASA has no intention of renaming it.

Why should the James Webb telescope be sent into space?

It was necessary to make JWST a space telescope and not a terrestrial one because this observatory requires very specific observing conditions. Earth’s atmosphere can obscure the images taken by the telescope because it is nearly opaque and shines in the infrared wavelengths that James Webb will observe. The technologies used in terrestrial telescopes do not currently allow this problem to be circumvented.

This need to send it into space makes the mission even more complex: all the mechanisms of the JWST must work perfectly.


JWST, in stowed position.  // Source: Northrop Grumman via Flickr (cropped photo)

Where is the James Webb Telescope located in space?

It took about a month for the telescope, after its launch, to reach its planned location: the Lagrange point L2, located about 1.5 million kilometers from our planet. It is important to place the JWST very far away because it needs a low temperature to function properly (-223°C). Its 5-layer shield helps keep it cool by blocking the light emitted by the Sun, Earth and Moon (which, by heating the telescope, could distort its observations).

But in addition to the shield, the position of the space telescope plays a role: It is located behind the Earth, in relation to the Sun. JWST is thus roughly aligned at all times with our planet and the Sun.

At such a distance, no repairs in space, like the maintenance missions that take place with Hubble, can be imagined.

How long will the James Webb Telescope mission last?

From its launch, the telescope was designed for its mission to last at least 5.5 years (including the first six months of its commissioning). Rather, the goal would be for its lifespan to exceed 10 years. Unlike the Hubble telescope, it is not so much the operation of its various components that is likely to be problematic over time. Rather, it is the amount of fuel that the observatory embarks on to maintain its orbit that will be crucial. JWST therefore carries enough fuel to operate for about ten years.


Final test of folding the wings of the primary mirror.  // Source: Northrop Grumman via Flickr (cropped photo)

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