James Webb Space Telescope—Fine Mirror Alignment Completed

With the completion of the “fine phasing” process, all of the 18 segments of the James Webb Space Telescope’s main mirror have been brought into alignment to act as a single large mirror, producing diffraction-limited images with the full aperture of the composite mirror.

For the alignment process, the telescope focused on a single star, which is shown here with the diffraction spikes due to the segmented mirror and support structure of the telescope. In the background, many faint galaxies can be seen (click image to display in full resolution). The alignment images were taken through a red filter to improve visual contrast.

This image may not appear impressive, but its purpose is engineering, not astronomy. To those who know what it represents, it is spectactular.

Compare the galaxies in the Webb image to those from among the best ground-based telescopes. This is the improvement Webb will deliver in everything it observes.