The James Webb Space Telescope has sent back its clearest image yet

New Scientist
SPACE 16 March 2022
By Leah Crane

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The James Webb Space Telescope focused on this bright star to align its mirrors

A crucial phase of mirror alignment has been completed for the James Webb Space Telescope, and the process resulted in the highest resolution infrared image ever taken from space

The James Webb Space Telescope (JWST) has reached a crucial phase in the alignment of its mirrors. Images from this process have shown that everything is working even better than expected, and the telescope’s operators say that its performance will be able to meet or even exceed the goals that were originally set for it.

JWST peers into the cosmos with the help of 18 gold-plated hexagonal mirrors. For it to work properly, all of these mirrors have to be aligned with extraordinary precision – within nanometres – so that they act as one. When the observatory sent back its first images in February, the mirrors weren’t yet aligned and the images were blurry. Now, although the alignment process isn’t quite complete, the image is crystal clear.

“This is as sharp an image as you can get from a telescope of this size,” said JWST scientist Marshall Perrin at the Space Telescope Science Institute in Maryland during a 16 March press conference. It is the highest resolution infrared image ever taken from space.

The picture itself shows a bright star called 2MASS J17554042+6551277*, 100 times fainter than the human eye can see — 2,000 light-years away. If the alignment hadn’t been precise enough, there would be multiple copies of the star in the image, but it shows that the mirrors are now all working together to create a single image of a star flanked by distant galaxies.

“The telescope performance so far is everything that we dared hope,” said JWST scientist Jane Rigby at NASA’s Goddard Space Flight Center in Maryland during the press conference. There are a few more alignment steps before the observatory can take its first science images, which are expected in June or July.

“We now have achieved what’s called ‘diffraction limited alignment’ of the telescope,” said Marshall Perrin, deputy project scientist for Webb at the Space Telescope Science Institute. “The mirrors are focused together as finely as the laws of physics allow, and this is the sharpest image you can get from a telescope of this size.”

As evidence of how well the telescope works, if you look closely at the image, background galaxies are visible, much like the “Deep Field” images taken by the Hubble Space Telescope.

“Basically, everywhere ever we look, it’s a Deep Field,” said Jane Rigby, Webb operations project scientist. “These engineering images are as sharp and crisp as images that Hubble can take, but at a wavelength of light that Hubble can’t see.”

Perrin said the team still needs to “dial in very small adjustments to bring the telescope to even more exquisite sharpness,” and added, “It’s an absolute thrill to say that everything has worked. At no point the process did we have any issues with any of the deployments, and while there were some surprises in the data, the outcomes are far closer to our hoped-for predictions than we could have expected.”

Webb has now completed steps four and five of the seven-step, three-month long alignment process.

“All 18 mirror segments are now aligned into a single mirror,” said Lee Feinberg, Webb’s optical telescope element manager. “The images came down over the weekend, it was a very emotional moment. We can see the optical performance of the telescope is absolutely phenomenal.”

Feinberg said the image is a 2,100 second exposure, and taking an image over that length of time allows the team to assess several aspects of the telescope’s performance. Not only are the optics working perfectly, but other systems are working well too. This includes the fine guidance sensors and reaction wheels that allow the telescope to point precisely and stay on target.

“We know it’s working because we have a picture of star that looks like star,” Feinberg said. “We’re getting close to the point where we can turn this observatory over to the scientific community.”

Here’s a great comparison of this star in approximately the same field of view as seen by another infrared telescope, Spitzer and then Webb:

The star 2MASS J17554042+6551277, is a “generic, anonymous, average star” chosen for its brightness – or lack thereof.

“We plucked this star out of obscurity,” Rigby mused, “It is 100 times fainter than what the human eye can see, but here it looks blindingly bright.”

The mirror alignment process, called phasing, began in early February and the seven different steps takes the mirrors’ initial placements after they were deployed to doing a “coarse” and then “fine” alignment, and then making sure the mirror works with all four of Webb’s instruments and their various fields of view.

“So far, we’ve nailed it,” Rigby said. “Webb is seeing back in time without really breaking a sweat. We’re still commissioning and have to align the telescope to the four science instruments, and get those instruments ready for prime time. We’ve already selected a year of compelling and demanding science with this telescope, and we’re all excited to get started.”

The scientists expect Webb to be fully commissioned by the end of June. One instrument, the MIRI or mid-infrared instrument still needs to continue cooling down to 7 K, or 7 degrees above absolute zero. It is currently at about 90 K.

* 2MASS J10430758+2225236 is a brown dwarf star located about 20 pc from Earth in Leo. It was discovered in 2007 by Adam J. Burgasser, Kelle L. Cruz et al. See: The Astrophysical Journal, 657:494–510, 2007 March 1 # 2007. The American Astronomical Society. All rights reserved. Printed in U.S.A. OPTICAL SPECTROSCOPY OF 2MASS COLOR-SELECTED ULTRACOOL SUBDWARFS



I am getting more excited every time I view images from the JWST. The background galaxies, only visible in far infrared, are fantastic and indicate what is to come in the future. I am thrilled!
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Looking pretty good. Should be an exciting year. I'm more interested in the close, unseen objects and densities that are near by. A more present time.

If only we had a super fast oscillator, we could beat(convert) all EM emission into the visual range and watch them. The universe is full of unseen light.

Hayseed -

If all the unseen light was visible at the same time, from far infrared to ultraviolet, wouldn't you be afraid of a sort of photonic overload? Your vision, and mind mine, would be one continuously bright field without any variations.
Just a few thoughts on your ideas.

You're absolutely right, it would blind us and make vision useless. But oscillators are like our eyes, and can only interact with a small section of spectrum at one time. An inherent property of oscillators. An ideal oscillator can only work at one frequency.

If we could build very fast oscillators, we could chop and sample light,(and other sub/atomic/molecular emissions) like we can with audio and other base band frequencies. This would allow us to detect very small changes in position and orientation. Mapping of atomic structure should be possible.

Molecular surgery or construction might be done with the appropriate emitter arrays. Chopping EM fields could also be used to position and orientate small objects, not just measure.them.