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NASA Reveals Phenomenal JWST Test Image As Preview Of What’s To Come

The test image is the deepest infrared image ever collected of hundreds of galaxies, but it's still far from the telescope's full capability.


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

The deepest infrared image ever taken of the universe using 72 exposures over 32 hours with the James Webb Space Telescope's Fine Guidance sensor
There's never been such a deep infrared image showing hundreds of galaxies using 32 hours of exposure. Image Credit: NASA, CSA and FGS team.

As space enthusiasts count down the days to the release of the first science-grade images from the JWST, NASA is helping whet people's appetite with the image above, which represents the deepest view of the universe ever taken in infrared.

The six points of the brighter stars in the field of view might be the first thing you notice, but the real significance lies in the abundance of galaxies, including the remarkable ring towards the bottom right.


Arguably, this is yet another example of Canadians getting the jump on their southern counterparts, since the image is a product of the Fine Guidance Sensor (FGS) – the Canadian Space Agency's contribution, which allows the telescope to lock onto faint objects.

The FGS isn't intended to capture images like this – most of what it records will be deleted, rather than waste valuable communications bandwidth. Instead, its role is to make sure the JWST is pointing in exactly the right direction so subsequent images and measurements can be perfect. However, during the commissioning stage, the JWST's operators are keen to establish all instruments' capabilities.

Over eight days in early May, the FGS aperture was used to take 72 exposures, overlapping on this part of the sky, with a total exposure time of 32 hours, confirming the telescope's capacity to maintain its orientation. The above image is the result of combining these for maximum depth.

The full image produced by combining 72 exposures taken using the Fine Guideance Sensor on the James Webb Space Telescope
The full image combining 72 overlapping exposures taken with the Fine Guidance Sensor of the JWST. Image Credit: NASA, CSA and FGS team

The FGS doesn't use color filters. Instead, this false color image uses red to represent the faintest objects and white to represent the brightest, with orange and yellow between. This deprives scientists of some of the important information the JWST's other instruments provide. For example, color reveals galaxies' ages, with younger ones being more blue from an abundance of hot young stars, while older galaxies are dominated by red stars.


On the right is the star 2MASS 16235798+2826079. It's so much brighter than anything else that its spikes dominate the image, despite the star itself being out of the field of view. As a demonstration of the JWST's immense power, this star has a magnitude of 9.3, meaning it is just visible under dark skies with a good pair of binoculars. At less than half the brightness of Neptune, it would be just another faint dot in a backyard telescope.

All of the JWST's instruments are now fully verified, other than the Near-Infrared Camera, which has one remaining mode under testing.

Anyone made suitably excited by this image has to wait another four days for the first full-color pictures to be released on July 12. The list of initial targets will be released later today, and you can watch their publication live at Webb First Images or on social media at 10:30 am EDT (2:30 pm UTC).


spaceSpace and PhysicsspaceAstronomy
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