The James Webb Space Telescope Has Taken Its First Images
After traveling nearly 1 million miles over the course of a month, the James Webb Space Telescope has not only arrived at L2, but is working on its final tasks prior to being fully operational. This includes aligning each of its 18 individual mirror segments and more. Just recently we saw some of the first progress photos from this event.
On Friday the 11th, a photo was released of not only some of the initial images from each mirror segment but a selfie of the primary mirror of Webb. These are quite incredible images as we can see the successfully deployed primary mirror around 1 million miles away. In addition, after focusing on a bright star, each mirror segment produced an image needed to match and align the primary mirror.
Webb is an extremely complex and interesting space telescope. Thanks to things like its massive size, it had to be folded to fit within the fairings of the Ariane 5 launch vehicle. This along with other reasons means each of the 18 mirror segments are not perfectly aligned. Currently, NASA is in the process of making each mirror perfect so Webb can produce incredible images.
The JWST Selfie
One of the most recent images taken that is quite incredible in the grand scheme of things is a picture of Webb itself. What many are calling the James Webb Space Telescope selfie, the next-generation space telescope was able to take a photo of its primary mirror and send it back to Earth. The last time we saw Webb was when the telescope separated from the upper stage of the Ariane 5. At that time it was fully folded to fit within the fairings. Over the next few weeks, Webb went through a long list of deployments including the primary mirror. NASA had received confirmation that the primary mirror had been deployed successfully, but that was based on mechanics within the telescope. This image shows us exactly how successful Webb has been up until this point. This “selfie” was created using a specialized pupil imaging lens inside of the NIRCam instrument that was designed to take images of the primary mirror segments instead of images of space. This specific camera along with the secondary mirror provided an extremely unique image.
This configuration is not used during scientific operations and is used strictly for engineering and alignment purposes. In this case, the bright segment was pointed at a bright star, while the others aren’t currently in the same alignment. This image gave an early indication of the primary mirror alignment to the instrument. It also gave everyone a fascinating image to look at. To be specific, this image helps NASA understand the alignment of the primary mirror to the camera itself and the instruments. Looking at this image, one of the features that stands out is the single mirror segment brightly lit up. The reason for this is that specific mirror segment is pointing at a bright star at the time of the selfie. As of right now the mirror segments are not properly aligned. This results in only a single segment looking directly at the bright star rather than all 18. You can also see the outline through the shadows of all 18 segments, and the outline of what’s in the instrument itself. All of which gives NASA a lot of valuable information in the general alignment process.
18 Pictures of One Bright Star
Not only did Webb take a picture of itself, but also 18 separate images of a single bright star. By now Webb is nearing completion of the first phase of the months-long process of aligning the observatory’s primary mirror using the Near Infrared Camera, or (NIRCam) instrument. There were two main challenges that the team faced. One was to confirm that NIRCam was ready to collect light from celestial objects, and then identify starlight from the same star in each of the 18 primary mirror segments. The result is an image mosaic of 18 randomly organized dots of starlight, the product of Webb’s unaligned mirror segments all reflecting light from the same star back at Webb’s secondary mirror and into NIRCam’s detectors. In order to do this, they first picked a very bright star that also didn’t have any stars near it that would contaminate the image.
As of right now, Webb is practically 18 separate telescopes because it is not yet aligned. This meant the team was expecting 18 separate images of this same bright star. From here the images were taken and NASA made a mosaic, then worked to find each of the 18 images of a single star. The agency pointed out that they were all very close and it was a promising result. Based on this mosaic, NASA was able to identify which of the 18 spots were from a specific mirror. This even includes specifics like which mirrors are on either of the wings of Webb. Once highlighted it’s clear to see in the image that one wing’s images are more closely grouped while the other is more spread apart. After identifying all of these 18 spots to each mirror segment they worked to make an array of them. Next is global alignment where each of the 18 spots begins to be aligned and focused. This is practically the last step prior to taking each spot and putting them on top of each other. This makes Webb a complete and aligned telescope. During the image capturing process that began Feb. 2, Webb was repointed to 156 different positions around the predicted location of the star and generated 1,560 images using NIRCam’s 10 detectors, amounting to 54 gigabytes of raw data.
The entire process lasted nearly 25 hours, but notedly the observatory was able to locate the target star in each of its mirror segments within the first six hours and 16 exposures. These images were then stitched together to produce a single, large mosaic as mentioned prior that captures the signature of each primary mirror segment in one frame. “This initial search covered an area about the size of the full Moon because the segment dots could potentially have been that spread out on the sky,” said Marshall Perrin, deputy telescope scientist for Webb and astronomer at the Space Telescope Science Institute. “Taking so much data right on the first day required all of Webb’s science operations and data processing systems here on Earth working smoothly with the observatory in space right from the start. And we found light from all 18 segments very near the center early in that search! This is a great starting point for mirror alignment.”
Conclusion
About a month and a half ago, Webb was launched into space heading to L2. Now after all this time it has made incredible progress. Just recently the next-generation space telescope took some of its first images. This included a selfie, along with 18 separate images of the same bright star. This allowed teams at NASA to stitch, observe, and match each image with an individual mirror segment. Very important steps in the focus and alignment phase of Webb’s progress. We will have to wait and see how the rest of the alignment process goes, and the quality of Webb’s upcoming images.
