James Webb Space Telescope's tantalising first images

After 25 years and over 10 billion US dollars, on Christmas Day 2021, the James Webb Space Telescope (JWST) was finally launched into space by a European Ariane 5 rocket.

With its 6.5-metre primary mirror and its tennis-court-sized sunshield, Webb had to be folded up to fit in the rocket’s fairing, only to be deployed step by step in the first two weeks of its mission.

Now, we're all eagerly awaiting the first proper images of space captured by the James Webb Space Telescope, which should be captured around June or early July 2022.

Find out how James Webb Space Telescope will study galaxies, and how James Webb Space Telescope will study exoplanets.

James Webb's latest image

The latest image from the James Webb Space Telescope shows an amazing view of the Large Magellanic Cloud, a satellite galaxy of the Milky Way.

The image was captured with JWST's coldest instrument: the Mid-Infrared Instrument, or MIRI.

Focussing on the star field of the Large Magellanic Cloud provides an opportunity for Webb scientists to test the telescope's imaging performance.

NASA has released a side-by-side pair of images showing how James Webb Space Telescope's capabilities compare to the Spitzer Space Telescope.

The now-retired Spitzer observatory captured hi-res images of the Universe in near- and mid-infrared.

"Webb, with its significantly larger primary mirror and improved detectors, will allow us to see the infrared sky with improved clarity, enabling even more discoveries," a NASA statement said.

James Webb Space Telescope has taken a new step towards beginning science operations in summer 2022.

Webb's image of 2MASS J17554042+6551277

After weeks of alignment, NASA finished focusing the James Webb Space Telescope's primary mirror on 11 March, achieving a precision that exceeds the original goal and resulted in the image below: an image of star 2MASS J17554042+6551277, released on 16 March 2022.

The image was significant because it showed that each of JWST's 18 primary mirror segments - which produce the space telescope's iconic 'honeycomb' mirror design - had been aligned correctly.

JWST had taken one more step towards beginning its exploration of the cosmos.

The milestone marked the end of a procedure known as ‘fine phasing’. JWST’s main mirror is made up of 18 hexagonal segments; to focus these the team pointed the telescope at a lonely star chosen to be easily identified, with few nearby companions.

They then adjusted each panel so that when combined, the 18 separate images were aligned into a single point of light, focused to within an accuracy of 50 nanometres – a fraction of the wavelengths of infrared light it will observe in.

Next, the team imaged the star with the Near Infrared Camera. Even though this was only meant to pick up the focused star, the telescope captured a scattering of background galaxies as well.

JWST's 18-star mosaic

The JWST team released an image in February 2022 showing 18 ‘different’ stars scattered across a black background.

In fact, the image - seen below - showed a single bright star in the constellation Ursa Major known as HD 84406.

The star was seen in 18 different positions because JWST’s mirror segments were still in the process of being aligned.

This seemingly chaotic capture was a result of JWST's unaligned mirror segments reflecting light back into the telescope's instruments, and was a vital part of preparing Webb for producing beautiful images of the Universe.

"We have aligned and focused the telescope on a star, and the performance is beating specifications," says Ritva Keski-Kuha, Deputy Optical Telescope Element Manager for JWST.

"More than 20 years ago, the JWST team set out to build the most powerful telescope that anyone has ever put in space and they came up with an optical design to meet the science goals," says Thomas Zurbuchen, Associate Administrator for NASA’s Science Mission Directorate

What next for James Webb Space Telescope?

The first in-focus image from one of JWST’s cameras is tantalising, tempting astronomers with the promise of future riches.

Compared to the previous infrared image of the region, from the Spitzer space telescope and WISE telescope, which showed an array of blobs, Webb’s image shows sharply focused galaxies that reveal structure in even these distant background sources.

With the exceptional resolution of JWST, we can piece together the life stories of these obscure galaxies.

Although we only have access to this single image, we know the camera will have imaged the field through many filters.

Looking at a galaxy’s brightness in each of these would allow us to make a good guess at its distance, and hence how far back in the Universe’s history we are seeing.

That’s not the point of these images, as more will be coming soon, but it’s a tempting idea!

So where is James Webb Space Telescope now, and when will science operations begin?

A total of three mid-course correction manoeuvres successfully placed the huge space telescope in a slow looping orbit around the second Lagrange point (L2), a stable gravitational point some 1.5 million kilometres behind Earth as seen from the Sun.

“But a lot more needs to be done before we can start science operations,” says Mark McCaughrean, the Senior Advisor for Science and Exploration at ESA (the European Space Agency), NASA’s main partner in the programme.

For one, the telescope and its sensitive instruments, which left the French Guiana launch platform at tropical temperatures, have to cool down to 230˚C below zero.

Thanks to its giant multi-layer sunshield, JWST had already reached –200 °C by early January 2022, but the passive cooling slows down over time.

It’s a delicate process, says McCaughrean. The optics can never be the coldest parts of the telescope, lest molecules released as gases from the graphite-composite support structure freeze down on the mirrors, degrading its performance.

When the NIRCam instrument (Near Infrared Camera) got cold enough for its sensitive mercury-cadmium-telluride detectors to pick up infrared light, the process of aligning the telescope’s 18 mirror segments could finally commence.

Each hexagonal segment is fitted with seven actuators and can be slightly tilted, shifted, rotated and deformed to ensure that they operate together as one perfect parabolic surface.

And since the alignment procedure is done with starlight, the image above marks JWST’s ‘first light’.

But it will take months of incremental precision adjustments before the 18 individual stellar images from each mirror are all brought together into one single focus.

Testing JWST's instruments

Around late April 2022, engineers will also start commissioning JWST’s four large science instruments:

• NIRCam (Near InfraRed Camera)
• NIRSpec (Near InfraRed Spectrometer)
• MIRI (Mid InfraRed Instrument
• FGS/NIRISS (Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph).

Equipped with beam splitters, filters and micro-shutters, all have different observing modes, and these have to be fully tested and calibrated before they are handed over to the astronomy community.

"Of course, every instrument has been tested and checked on Earth," says McCaughrean, "But we need to prove that they also perform flawlessly in space."

When will we see James Webb Space Telescope's first proper images?

So what about that supposedly awe-inspiring first picture taken by the James Webb Space Telescope? JWST's first images are not expected until some six months after launch, which would be late June or early July 2022.

"What it will show is a closely guarded secret. Most likely some kind of star-forming region," says McCaughrean.

The first round of science observations won’t start before summer 2022.

Astronomers can’t wait to train their new, expensive toy on their favourite objects, be that a remote galaxy at the dawn of time, a planet-spawning accretion disk, an exoplanet’s atmosphere or a denizen of our own outer Solar System.

James Webb Space Telescope has less pointing flexibility than the Hubble Space Telescope.

Since the telescope must face away from the Sun to keep its instruments consistently cool, its ‘field of regard’ will cover 40% of the sky on any given day, and it will take around 6 months to access the whole of the sky.

JWST’s mid-course corrections used up less fuel than expected, which means there’s more left to keep the space telescope in its L2 orbit.

As a result, its operational lifetime may be extended beyond the projected operational period of 10 years.

How the James Webb Space Telescope unfolded in space

It took more than 50 individual steps and two weeks to for JWST to reach its orbital point and become fully deployed.

Here's a timeline of how it all took place.

1. 25 December 2021, 12:20 UT: JWST launches from the Guiana Space Centre on an Ariane 5 rocket; after 27 minutes, it separates from the launcher’s upper stage to travel to L2 alone.
2. 25 December 2021, 12:48 UT Deployment of JWST’s 6m, five-panel solar array, which delivers about 1Kw of power. The telescope can now switch from battery power to its own power.
3. 26 December 2021: Deployment of the high-gain communications antenna, which allows communication with Earth through NASA’s Deep Space Network.
4. 28 December 2021: The Forward Unitized Pallet Structure (UPS), which supports and contains the five folded layers forming the front half of the sunshield, is lowered into place.
5. 29 December 2021: The Deployable Tower Assembly (DTA) is raised by 1.2m for better thermal isolation and to give room for the sunshield to unfold in front and behind.
6. 30–31 December 2021: Sunshield mid-booms are extended on either side, pulling the folded sunshield layers with them, to form the first part of its distinctive 21m x 14m kite shape.
7. 3–4 January 2022: The five Kapton layers of Webb’s sunshield are tensioned. While the Sun-facing side endures temperatures up to 90°C, the shielded side will be as cold as –230°C.
8. 5 January 2022: JWST’s 74cm convex secondary mirror is deployed. The foldable structure supporting it has been dubbed “the world’s most sophisticated tripod”.
9. 6 January 2022: Deployment of the 1.2m x 2.4m Aft Deployable Instrument Radiator (ADIR), which radiates heat from the space telescope’s science instruments into space.
10. 7–8 January 2022: Deployment of the two side panels forming JWST’s 6.5m primary mirror. Its 18 hexagonal segments are made of lightweight beryllium coated with pure gold.

This article originally appeared in the March 2022 issue of BBC Sky at Night Magazine.