A major milestone has been achieved in the deployment of the James Webb Space Telescope, with an instrument on board detecting its first photons from a distant star. This means engineers can now begin the three-month process to align the space telescope’s 18 mirrors.
After years of delays and a seemingly endless succession of hiccups during development, the $10 billion Webb mission, now in its seventh week, has been smooth as silk. The painstaking process of deploying the space telescope and preparing it for innovative astronomy has progressed as smoothly as anyone could have hoped, with the most recent achievement being the telescope’s first starlight detection, which occurred earlier this week.
“This milestone marks the first of many steps in capturing images that are initially out of focus and using them to slowly adjust the telescope,” NASA said in a statement. statement announcing the achievement on Thursday. “This is the beginning of the process, but so far the initial results match expectations and simulations.”
This inaugural batch of photons was detected by Webb’s Near Infrared Camera (NIRCam) instrument. The photons came from HD 84406, a star located nearly 260 light-years away and visible in the constellation Ursa Major. With this starlight detected, the team can now begin the three-month process of arranging all 18 panels so that they form a single concave mirror.
Launched on December 25, 2021, the Webb Space Telescope is a collaboration between NASA, ESA and the Canadian Space Agency. Once operational, Webb will search for light from the first stars and galaxies, study galaxy formation and evolution, and scan the atmospheres of distant exoplanets, among other astronomical and astrobiological goals.
Webb reached its stable orbital point, Lagrange Point 2, on Jan. 24, 2022. Since then, engineers have finished turning on its science instruments and turning off its heaters, which they did to start a prolonged cooling process. The heaters were necessary to keep Webb’s optics warm and to prevent condensation of water and ice. The alignment process could begin once the instrument reached -244 degrees Fahrenheit (-153 degrees Celsius), according to NASA.
The alignment process will consist of seven different steps, such as segment image identification, segment alignment, and image stacking. Full details of these steps can be found here. But as NASA explains, this work will require extraordinary precision:
To work together as a single mirror, the 18 segments of the telescope’s primary mirror must match each other within a fraction of a wavelength of light, about 50 nanometers. To put this into perspective, if Webb’s main mirror were the size of the United States, each segment would be the size of Texas, and the team would have to align the height of those Texas-sized segments with each other to an accuracy of about 1.5 inches.
Engineers will use the data collected by NIRCam to gradually align the telescope. Since the large mirror is not yet aligned, the incoming photons produced an image showing 18 fuzzy points of light. The team will keep Webb trained on HD 84406 and work to produce a single, focused image of the star. NASA warns that the images collected throughout this three-month process will be strictly utilitarian in nature and not “pretty,” and also a pale comparison to what we can expect next summer.
The end of this process will see a fully aligned telescope and the beginning of the next phase: instrument commissioning. Fingers crossed that these important next steps go as planned and that we see spectacular results starting in June.