Space

James Webb Space Telescope snaps first images – a star and a selfie

James Webb Space Telescope sna...
A render of the James Webb Space Telescope
A render of the James Webb Space Telescope
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The first image from the James Webb Space Telescope is a mosaic made up of 18 images of the same star, as taken by each of the 18 mirror segments which are currently unaligned.
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The first image from the James Webb Space Telescope is a mosaic made up of 18 images of the same star, as taken by each of the 18 mirror segments which are currently unaligned.
A selfie of the James Webb Space Telescope's primary mirror segments, as snapped by the NIRCam
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A selfie of the James Webb Space Telescope's primary mirror segments, as snapped by the NIRCam
A render of the James Webb Space Telescope
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A render of the James Webb Space Telescope
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The James Webb Space Telescope has taken its first images of space. What looks like a smeared starfield is actually the same star snapped 18 times, as the mirror segments try to align themselves to focus on the star. The craft also took a selfie of its mirrors to help align them.

The JWST is made up of a tennis court-sized array of 18 golden mirrors, but after launch and deployment, they’re all pointing in slightly different directions. Before the telescope can begin probing the depths of the cosmos, these mirrors need to be brought into alignment so they can focus on the same object.

The first such object is a star known as HD 84406, located in the constellation Ursa Major. It was selected for this calibration job because it’s bright and isolated from other stars, making it easy to identify. To find it, the telescope was pointed to 156 different positions around the predicted location – an area of sky about the size of the full Moon – generating 1,560 images. Then, the data was scanned until the star had been located in images from all 18 mirror segments. These 18 images were then stitched together into one mosaic.

The first image from the James Webb Space Telescope is a mosaic made up of 18 images of the same star, as taken by each of the 18 mirror segments which are currently unaligned.
The first image from the James Webb Space Telescope is a mosaic made up of 18 images of the same star, as taken by each of the 18 mirror segments which are currently unaligned.

From this data, the team can determine the alignment positions of each mirror segment. Over the next few weeks, the positions of the mirrors will be adjusted until the 18 stars merge into one.

“Launching Webb to space was of course an exciting event, but for scientists and optical engineers, this is a pinnacle moment, when light from a star is successfully making its way through the system down onto a detector,” said Michael McElwain, a project scientist for the JWST.

Another perspective will help with this alignment process. A lens inside the NIRCam instrument is pointed back towards the primary mirror segments, allowing the spacecraft to take selfies for engineering purposes. In this shot, the bright segment is currently pointed towards the star, while the others aren’t in the same alignment.

A selfie of the James Webb Space Telescope's primary mirror segments, as snapped by the NIRCam
A selfie of the James Webb Space Telescope's primary mirror segments, as snapped by the NIRCam

These images constitute major milestones in James Webb’s progress, but aesthetically they’re pretty underwhelming. The real money shots will arrive mid-year, after all the alignments are complete and the instruments are cooled to their cryogenic operating temperatures.

The team describes the alignment process in the video below.

Photons Received: Webb Sees Its First Star – 18 Times

Source: NASA

View gallery - 3 images
5 comments
5 comments
noteugene
I'm hoping they get the mirrors aligned sooner than expected. Been looking forward to looking back to the point of creation since they first announced the JWST. I have one question that I haven't seen an explanation for. Why were they not enabled to construct the telescope to see all the way back to the beginning? Maybe there has been an explanation for that but I've not seen it.
guzmanchinky
And if it had failed it would be all over the news. And since it works no one outside of science cares. And that is what is wrong with our world today.
Ornery Johnson
This initial alignment was considered closer than expected, and a much larger area was imaged in anticipation that some mirrors could be much further out of alignment. Given that, I'd expect the alignment to be completed earlier than expected.
c2cam
@guzmanchinky - Couldn't agree more!
Slowburn Fan
Selfie? How would the nirCam be able to take that picture? In the image, you can see the three tripod legs converge to common point. It wouldn't be able to see that. Does it have a selfie stick? It doesn't make sense