NASA engineers working to align the 18 hexagonal mirrors of the James Webb Space Telescope have released its first pictures. One shows the same star appearing 18 times, while a camera also took a ‘selfie’ of the mirrors
11 February 2022
The James Webb Space Telescope (JWST) has turned its instruments on and taken its first pictures in space. Engineers are in the process of aligning the telescope’s 18 gold-plated mirrors so that it can peer into deep space, and to do so they have taken images using one of its infrared cameras.
The telescope launched on 25 December 2021 and arrived at its final orbit a month later, unfurling from its initial folded-up position on the way. Once the scientific instruments cooled down enough to be operated safely, they were turned on and researchers began to calibrate them.
“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 JWST scientist at NASA’s Goddard Space Flight Center in Maryland, in a statement.
The calibration of the mirrors is one of the most important tasks for the telescope, as they all have to be perfectly aligned if it is going to take clear images. The telescope has now taken two images to help with that process.
The first, pictured at the start of this article, is a “selfie” of the mirrors themselves. In this image, one of the segments appears much brighter than the others, which is because it is pointed directly at a bright star, while the others aren’t yet in the same alignment.
The second image, pictured directly above, shows a star called HD 84406 in the constellation Ursa Major, also known as the Big Dipper. The picture is a mosaic made up of 1560 individual shots, showing 18 copies of the star, one from each of the mirrors. When they are aligned, all the segments will work as a single mirror and those 18 copies will be right on top of each other.
This allows the telescope to add the light reflected by all the segments together so that it can spot fainter and more distant objects. “This is a great starting point for mirror alignment,” said JWST scientist Marshall Perrin at the Space Telescope Science Institute in Maryland. The process of alignment is expected to take about three months, after which JWST will begin taking images of exoplanets, stars and distant galaxies.
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