Snapshot: The James Webb Space Telescope sees stars

The first stage of aligning the telescope's mirror segments is complete.
By | Published: February 24, 2022 | Last updated on May 18, 2023
The image is a mosaic of 18 versions of the same star arrange in the shape of a hexagon taken by the James Webb Space Telescope.
NASA/STScI/J. DePasquale

The James Webb Space Telescope (JWST) has opened its eyes to the stars. The mosaic is of a single star repeated in 18 images to bring the telescope’s 18 hexagonal mirror segments into alignment. NASA announced the blurry star pictures were collected by the instrument earlier this month. 

While nowhere near the breathtaking images we expect from the telescope later this year, this alignment is a crucial step in getting the individual segments to act as one mirror. The completed first stage of the process is  called “Segment Image Identification.” 

To collect the data from the stars, the telescope was adjusted in 156 positions in prediction of the star’s location in an area “about the size of the moon,” according to Marshall Perrin, deputy telescope scientist for Webb and astronomer at the Space Telescope Science Institute in press release. Within the first six hours, researchers were able to identify the target star and then the images were formed into one composite picture. The process took 25 hours and, in total, Webb collected 1,560 images of the star. 

Now that the image is arranged in the correct order, the second phase of the project, called “Segment Alignment,” will begin. This phase will bring the stars into focus by correcting any large mirror setting errors.

The final phase, “Image Stacking,” will bring the 18 individual spots of light to one point, creating a single image. Completion is expected in the next several weeks. And, soon after, JWST will kick start its science discovery missions