James Webb: 13 questions to understand the space telescope mission

The James Webb Space Telescope (JWST) is located 1.5 million kilometers from Earth. In mid-July 2022, the first official photos of the observatory were released. The result is beautiful. Hubble’s replacement is assured.

James Webb finally shows what he can do. The space telescope, which is now located 1.5 million kilometers from the Earth, took the first historic photo of the bottom of the Universe, which was released on July 11, 2022. The event is so historic that even Joe Biden, the President of the United States , joined the festivities. Even in France, Emmanuel Macron went there with his tweet.

Then on July 12, the observatory delighted astronomers, the public and journalists more than snapshots showing the remains of a dying star, a cosmic ballet between four galaxies, the secrets of a giant exoplanet and what looks like cosmic cliffs – where stars are born. , in vast nebulae. These shots of James Webb are confusing.

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

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

What about the James Webb Telescope?

It’s over: the James Webb telescope is in space! The launch was successful on December 25, 2021. It remains to be fully operational. In total, more than 300 critical points were identified as potentially problematic during its deployment; obviously, they are closely monitored by NASA.

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What is the James Webb Telescope for?

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

  • Detect the light of the first galaxieswhich appeared shortly after the Big Bang,
  • Study the formation and evolution of galaxies,
  • More understandable the birth of the stars,
  • Likewise exoplanets.

For this, JWST observes in the infrared range (which is radiation between visible light and microwaves) and in space. Therefore, the observatory will be able to go far back into the Universe’s past, to see the first galaxies in formation – “young galaxies” – and to examine the interior of the dust clouds where the stars and planets formed.

What are the instruments of the James Webb Telescope?

The observatory has four scientific instruments on board:

  • A near the infrared camerathe NIRCam (for “Near-InfraRed Camera”), which among other things can detect stars that appeared after the Big Bang, search for supernovae, measure the distorted light caused by dark matter,
  • A near infrared spectrometerthe NIRSpec (“Near-Infrared Spectrometer”), which allows for example the study of the chemical elements of distant galaxies or clusters of young stars,
  • A mid-infrared instrumentthe MIRI (“Mid Infrared Instrument”), where it is possible to observe brown dwarfs, exoplanets and the evolution of stars and protoplanetary systems,
  • And one near infrared imager and slitless spectrographsaid NIRISS (“Near Infrared Imager and Slitless Spectrograph”), which will help study exoplanets and distant galaxies.

Why does the James Webb Telescope have a single-sided mirror?

The beautiful main mirror of the James Webb telescope, with an approximate diameter of 6.5 meters, is not noticeable for its golden color and its 18 parts assembled in a hexagonal shape. In astronomy, the mirror is said to be divided. This is not a technical choice, because it is possible to build it in a block.

It is a logistical motivation that hides behind this choice: it is impossible to fit a mirror of this size composed of a rocket block that launched the JWST into space. For the first time, it was decided to launch a telescope with a split mirror into space.

Will the James Webb Telescope replace Hubble?

It is not entirely accurate to say that the James Webb Space Telescope is intended to replace the Hubble. You should see him as more than an heir. True, JWST exceeded a limit of Hubble, which was unable to see beyond the near-infrared (so it will return less far into the past than JWST). It is also larger in size than the Hubble.

But the day Hubble stops working, the James Webb telescope will have no way to completely replace it. Currently, Hubble is the only telescope capable of observing the ultraviolet 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. Eventually, its launch took place on Christmas Day, December 25, 2021.

Where did the James Webb Telescope come from?

It took off from the Kourou space center in French Guiana, aboard an Ariane 5 ECA rocket. The observatory had to be transported by ship 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 beginning of the project, this budget has been constantly revised upwards.

NASA mentioned that it participated in the total cost of JWST in the amount of 7.998 billion dollars. He estimated that the first five years of operation of the observatory, added to the two years needed for the exploitation of its data, would generate an additional cost of 8.835 billion dollars – knowing that the JWST should double its life .

Why was the launch of the James Webb Telescope postponed?

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

And since then, the take-off has been postponed continuously. The covid-19 pandemic has significantly disrupted the work flow, forcing the space launch date to be postponed until 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 provisional name “Next Generation Space Telescope” (NGST, for “Next Generation Space Telescope”). It is named as such to symbolize the continuity of its activities, compared to Hubble.

JWST received its official name on September 10, 2002, referring to James Webb (1906-1992), the second administrator of NASA. He is known for leading Apollo. However, this choice of name is questioned by many and many scientists, because James Webb favors a policy to exclude LGBTQI + people within the space agency. NASA isn’t looking to rename it, though.

Why should the James Webb Telescope be sent into space?

It is necessary to make JWST a space telescope, and not a terrestrial one, because this observatory requires very specific observation conditions. The Earth’s atmosphere can blur the images captured by the telescope, because it is almost opaque and emits infrared wavelengths where James Webb will observe. Technologies used in terrestrial telescopes currently do not allow this problem to be avoided.

This need to send it into space makes the mission all the more complicated: all the JWST mechanisms must work.

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

Where is the James Webb Telescope placed 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 shield, made up of 5 layers, helps to cool it, by blocking the light emitted by the Sun, Earth and Moon (this, by heating the telescope, distorts its observations).

But in addition to the shield, the position of the telescope in space plays a role: it is placed behind the Earth, relative to the Sun. JWST is thus almost in sync with all the times of our planet and the Sun.

At such a distance, there is no maintenance that can be imagined in space, such as the maintenance missions that take place on Hubble.

How long will the James Webb Telescope mission last?

From its launch, the telescope is designed for its mission to last at least 5.5 years (including the first six months of its commissioning). The goal is that its life will exceed 10 years. Unlike the Hubble telescope, the operation of its various components is less likely to become problematic over time. It is rather the amount of fuel that the observatory starts to maintain its orbit that is decisive. So the JWST carries enough fuel to last for about ten years.

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Final attempts to fold the wings of the main mirror.  // Source: Northrop Grumman via Flickr (cropped photo)

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