Remember him, that ‘failed’ picture from the James Webb Space Telescope? It now looks a lot better. Just still don’t expect a picture like you are used to from the Hubble Space Telescope.
In the photo we wrote about on Feb. 11, a single star showed up as a random-looking swarm of bright spots. Each speck of light corresponded to one of the eighteen hexagonal segments of the primary mirror of the James Webb telescope launched late last year.
After the team behind the space telescope figured out which version of the star belonged to which mirror segment, they were able to show the spots ‘in formation’. This resulted in this so-called image array on, released on February 18†
The eighteen individual figurines in the photo above are not really great. Remember that you are looking at a star, which should appear as a single point of light. To get closer to that, the Webb team fine-tuned the eighteen segments even more. It also manipulated the second mirror, where the eighteen segments direct their light. That phase, Segment Alignment, already resulted in a much sharper image:
But then again, we don’t want eighteen separate images of the same star, each made by a small hexagonal mirror. What we want is one image. The Webb researchers achieved this during the phase called Image Stacking – the ‘stacking’ of images. We do, however, look at the sum of the work of eighteen small mirrors; they do not yet work together like one big mirror.
Adjusting the mirrors is therefore not yet ready. The whole process is divided into seven phases, of which Segment Alignment and Image Stacking were number two and three. There will therefore be four more steps in the coming weeks, in which the spot in the middle should become increasingly sharp.
In total, the tuning will take about three months, the Webb team recently reported in a blog post† After that, the instruments on board the space telescope can be put into use.
In other words: the really beautiful pictures, as we are used to from other space telescopes, will take a while. But it’s also fascinating how we can track all the way there this time around.
Source material:
†Webb Mirror Alignment Continues Successfully” – NASAN
†Webb Team Brings 18 Dots of Starlight Into Hexagonal Formation” – NASA
†Photons Incoming: Webb Team Begins Aligning the Telescope” – NASA
Images in this article: NASA/STScI