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James Webb telescope © NASA/Getty

James Webb Space Telescope: everything you need to know about the Hubble successor

Published: 05th May, 2022 at 10:30
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The James Webb Space Telescope is almost ready to begin its mission.

The James Webb Space Telescope (JWST) has been powering through its deployment and alignments, so far proceeding without any problems and even performing above expectations.


After reaching its final destination and deploying its instruments, the JWST has now completed all of its alignments, meaning it is fully focused and able to take pin-sharp imagery. All that is left now is for the instruments to be properly calibrated.

The successor to the Hubble Space Telescope, NASA’s new and much-improved space observatory has several goals in mind for its trip into space. Not only will it be used to deepen our understanding of the Milky Way, but it will also peer at faraway exoplanets and celestial objects, and hunt for evidence of dark matter.

But what stage is the James Webb Space Telescope at now, how does it differ from Hubble and who is James Webb, the man the telescope is named after? We've answered these questions and more below.

Where is the James Webb Space Telescope now?

The James Webb Space Telescope is now in L2 Orbit - its final destination, about 1.5 million kilometres from Earth. This is a journey that took roughly a month to complete.

You can track its progress with NASA's 'Where is Webb' feature. Not only does this show the current distance from Earth but also the telescope's speed, temperature, how long it has been in orbit and what its next stage is.

© Adriana Manrique Gutierrez, NASA Animator
An artist conception of the JWST © Adriana Manrique Gutierrez, NASA Animator

What are the most recent updates from the JWST?

The JWST has gone through a number of key stages to get to where it is now. After travelling to its end destination, it has since deployed its instruments, cooled down, aligned its telescope and even taken a number of pictures.

Now, the telescope has performed all of its adjustments and is fully focused and aligned. The next step is for the instruments to be properly calibrated. This simply means making sure they are delivering their data in a way that is understood.

This will likely take the next couple of months. After that, the JWST will finally be ready to begin its mission, taking photos and exploring the mysteries of space.

First images from the telescope

NASA has now released a few images from the JWST throughout its development. For the first sets of images, these were by no means clear photos or even a hint at the telescope's full power. The first images came on 11 February 2022 and took a whole week to capture. It is a mosaic made up of 1,560 images amounting to 54GB of raw data.

A mosaic of 1560 images from JWST © NASA

As the telescope advances through its alignment, it is able to send back more detailed images. The team were able to create an image using 18 scattered dots of starlight, moved into a hexagonal shape (the same relative locations as the physical mirrors). The team refined each mirror's image by making minor adjustments, while also changing Webb's second mirror's alignment.

These focused dots were then stacked on top of each other. During this process, called image stacking, the team activated six mirrors at a time, commanding them to repoint their light to overlap until all dots of starlight overlapped each other. This results in one single clear image of a star.

(Left) Image during segment alignment (right) same image after image stacking © NASA

More recently, as the telescope completed more key alignment stages, the JWST was able to send back an alignment evaluation image. This meant they could fully focus on a test star with pinpoint accuracy. While this is an indication of the future of the telescope's imagery, the team has cautioned that there is still a lot of work to be done before it is fully operational.

The first fully focused image from the JWST © NASA

After completing all of its alignment phases, the JWST sent back crisp and well-focused images using all four of its science instruments.

This means that the telescope has passed image sharpening checks and just needs to calibrate over the next few months. At this point, the telescope will be fully operational.

Images taken using the fully aligned instruments © NASA

When did the James Webb Space Telescope launch?

An Ariane 5 rocket during launch in 2017 © Getty
An Ariane 5 rocket during launch in 2017 © Getty

The James Webb Space Telescope was launched on Christmas Day 2021.

If you were too busy opening presents and enjoying a Christmas dinner to watch the launch on television, you can view the launch again on the JWST YouTube channel.

While the telescope has now officially launched, it saw a huge number of delays to get to this point. The observatory was originally expected to launch back in 2007. Since then, it has experienced over 16 launch delays with the pandemic extending the date way past the last expected date of March 2021.

The telescope was launched on the Ariane 5 rocket. This is a specialised rocket designed to take satellites and other payloads into transfer or low-Earth orbit.

Who is James Webb?

James Webb in 1966 © Getty
James Webb in 1966 © Getty

You might be thinking, who gets the honour of having such a historic telescope named after them? Well, that title goes to James Edwin Webb, the second administrator of NASA, best known for heading up Apollo – the first space programme to send humans to the Moon.

He was also instrumental in the two crewed space programmes that followed on from Apollo: Mercury and Gemini. While Webb did eventually die in 1992, aged 85, he left a massive legacy behind, deserving of a telescope named after him.

“It is fitting that Hubble’s successor be named in honour of James Webb. Thanks to his efforts, we got our first glimpses at the dramatic landscape of outer space,” said former NASA administrator Sean O’Keefe about the observatory’s name. “He took our nation on its first voyages of exploration, turning our imagination into reality.”

The telescope hasn’t always been named after Webb. It started its life being known as the Next Generation Space Telescope which, realistically, isn’t the most imaginative name we’ve ever heard!

How big is the James Webb Space Telescope?

NASA employees stand by a full-scale replica of the James Webb Telescope © NASA
NASA employees stand by a full-scale replica of the James Webb Telescope © NASA

Billed as the successor to the Hubble Space Telescope, the JWST is the largest space observatory ever built. Its gigantic sun shield base measures a massive 22m by 12m, roughly the same size as a tennis court.

Although nearly twice as big as Hubble (which is only 13m long), the JWST is almost half the weight at 6,500kg.

The JWST’s gold-plated mirrors have a total diameter of 6.5m, much larger than Hubble’s 2.4m diameter plate. Overall, the JWST will have approximately a 15 times wider view than Hubble.

How far can the James Webb Space Telescope see?

Using its infra-red telescope, the JWST observatory will examine objects over 13.6 billion light-years away.

Because of the time it takes light to travel across the Universe, this means that the JWST will effectively be looking at objects 13.6 billion years ago, an estimated 100 to 250 million years after the Big Bang. This is the furthest back in time ever observed by humanity.

Where will the James Webb Space Telescope orbit?

After launching into space, the JWST will orbit the Sun, flying up to 1.5 million kilometres from Earth in temperatures reaching -223°C.

For comparison, the Moon is 384,400km away, while the Hubble Space Telescope flies only 570km above our planet. As the JWST will operate so far away from Earth, it will not be able to be serviced by astronauts if any faults arise.

What is the James Webb Space Telescope's mission?

© alex-mit Getty Images
James Webb telescope 3D illustration © Alex Mit Getty Images

As the JWST is a product of an international collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA), it has many mission goals.

These include:

  • Examine the first light in the Universe and the celestial objects which formed shortly after the Big Bang.
  • Investigate how galaxies form and evolve.
  • Study the atmospheres of distant exoplanets.
  • Capture images of planets in our own solar system.
  • Locate evidence of dark matter.

The JWST is expected to operate for five years after its launch. However, NASA hopes the observatory will last longer than 10 years.

Unfortunately, the observatory won’t be able to operate forever: although mostly solar-powered, the JWST needs a small amount of finite fuel to maintain its orbit and instruments.

How is the James Webb Space Telescope different to Hubble?

© NASA/MSFC/David Higginbotham/Emmett Given
James Webb telescope mirrors © NASA/MSFC/David Higginbotham/Emmett Given

The James Webb is seen in many ways as an improved successor to the Hubble telescope which was launched way back in 1990. But are they similar or are these two telescopes drastically different?

Firstly, both telescopes see light in different ways. The Hubble’s main focus is on both visible and ultraviolet light. While it can observe a very tiny portion of the infrared spectrum, it is nowhere near the extent to which the JWST can.

The JWST is specifically designed to focus on the infrared spectrum. It can’t see in ultraviolet light as Hubble can, but it will be able to focus on bright objects like very distant galaxies.

The James Webb Telescope is also much larger than the Hubble, mostly due to its large sunshield. This is used on all space telescopes but is especially important with the James Webb due to its infrared cameras. If it isn’t kept cool, it could risk blinding itself to the lights of objects it is trying to observe.

One other key difference between the two satellites is the distance that they will be kept. The Hubble telescope orbited above Earth’s atmosphere but was near enough to be approached if repairs needed to be done.

The JWST on the other hand will be far away, around 1.5 million kilometres away! That’s both further than any human has ever travelled and too far for anyone to ever go repair the satellite if something goes wrong.

It will be this far out for a few reasons. It will be in a place where the gravity of the Sun and Earth work together to help keep the satellite in place, plus it will be far away from the reflected radiation of the Earth, helping keep it cool.

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Alex is a staff writer at BBC Science Focus. He has worked in technology and science journalism since graduating in 2018 with an interest in consumer tech, robotics, AI and future technology.


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