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NASA has published the first images taken with the James Webb Space Telescope. For the time being, these are blurry images of a star, because the mirror segments are not yet aligned. An image has also been made of the mirror, as if it were a selfie.
NASA says very happy to hear confirmation that light from a star has made its way to the Near-Infrared Camera, or NIRCam, one of the telescope’s instruments. The first images identified light from the same star at each of the eighteen hexagons that make up the primary mirror. The result is now another mosaic image with eighteen random points of light from the same star. According to NASA, this result corresponds quite well with expectations and simulations.
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Two of the same images, with each dot on the left labeled with the specific mirror hexagon responsible for that dot.
There are now eighteen images of the star instead of a single one, because the hexagons are not yet aligned. As a result, they all reflect the light from the star in their own way, after which it falls on the secondary mirror and then on the detectors of NIRCam. Now the process begins in which all hexagons are moved in very small steps, possibly also slightly adjusting the curvature. This is necessary to eventually get to the point where all eighteen images merge into a single image of the same star. Currently James Webb has eighteen individual mirrors, as it were, all doing their own thing, but slowly they are being aligned so that they operate together as a whole.
During the image acquisition, which began on Feb. 2, the telescope was pointed at 156 different positions around the star’s expected location. With the ten detectors of NIRCam, 1560 images were taken in a period of 25 hours, good for 54 GB of raw data in total. During the first six hours and 16 images taken, the star was seen at each of the 18 mirror segments. Those images were then merged to form a large mosaic. The images with the eighteen dots is a cut-out from the center of this mosaic.
The target used is the star HD84406 located 260 light-years from Earth. It is located in the Ursa Major constellation, but is just too dim for the naked eye to see. HD84406, however, is too bright to be studied by Webb once the telescope is completely ready and able to get objects into sharp focus. Partly because of its fierceness, however, it is an ideal target for the current process of data collection and alignment of all individual hexagons. In addition, HD84406 was a suitable candidate, because the object is easy to identify and is quite isolated in the sky.
The ‘selfie’ was taken by a special pupil imaging lens within the NIRCam instrument. That part is designed to create images of the segments of the primary mirror rather than objects in the Universe. This configuration will not be used for scientific missions in the future and will only be useful now to support alignment. The above image shows a bright hexagon aimed at a bright star, while the other segments were not aligned in the same way at the time.
De James Webb Space Telescope was successfully launched on December 25 and a month later he arrived at his destination: orbiting the second Lagrange point about 1.5 million kilometers from Earth. During that journey, the sun shield and wings with the mirror segments on the side have successfully unfolded. The first real images for scientific purposes are not expected until the summer.
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