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Star twinkles 18 times in new James Webb Space Telescope image

A single star repeats in a hexagonal pattern in this image during James Webb Space Telescope's alignment, released on Feb. 18, 2022.
A single star repeats in a hexagonal pattern in this image during James Webb Space Telescope's alignment, released on Feb. 18, 2022. (Image credit: NASA/STScI/J. DePasquale)

The James Webb Space Telescope finished the first major stage in its long process of aligning the observatory's 18-segmented primary mirror.

A single star that the observatory looked at was deliberately rendered 18 times into a hexagonal shape. Eventually, those 18 images will perfectly align into a single, sharp focus, but the interim result portrays a star repeated perfectly in a hexagonal pattern reminiscent of a stunning celestial snowflake.

"The resulting image shows that the team has moved each of Webb’s 18 primary mirror segments to bring 18 unfocused copies of a single star into a planned hexagonal formation," NASA officials wrote in a blog post Friday (Feb. 18).

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The star images are steered into this particular pattern "so that they have the same relative locations as the physical mirrors," Matthew Lallo, systems scientist and telescopes branch manager at the Space Telescope Science Institute, which manages Webb, said in the release.

Next, the observatory will begin what engineers call "segment alignment," which will fix any larger positioning errors in the individual segments of the primary mirror and update the secondary mirror's alignment.

Once segment alignment is finished successfully, the team will start the third phase — "image stacking" — that will ultimately bring the 18 images on top of each other into one clear view. 

Lallo said the three-phase procedure will allow the team to experience "an intuitive and natural way of visualizing changes" throughout the process. Another benefit, he added, is "we can now actually watch the primary mirror slowly form into its precise, intended shape."

Properly aligning the mirrors is a main goal of Webb's commissioning, which is expected to conclude in the summer. The mission launched Dec. 25, 2021, with an ambitious mission to look at the early universe, exoplanets and other points of interest in the cosmos.

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Elizabeth Howell
Elizabeth Howell

Elizabeth Howell, Ph.D., is a contributing writer for Space.com since 2012. As a proud Trekkie and Canadian, she tackles topics like spaceflight, diversity, science fiction, astronomy and gaming to help others explore the universe. Elizabeth's on-site reporting includes two human spaceflight launches from Kazakhstan, and embedded reporting from a simulated Mars mission in Utah. She holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, and a Bachelor of Journalism from Canada's Carleton University. Her latest book, NASA Leadership Moments, is co-written with astronaut Dave Williams. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday.