James Webb Space Telescope brings star into focused image for first time

At the beginning of February, James Webb Space Telescope captured its very first images. Now the 18 mirrors have been aligned, bringing the star to a single, in focus point.

NASA released the latest image just before a virtual briefing on the telescope’s progress, which is set to begin at noon today.

The James Webb Space Telescope has been in development for a long time, but since its launch on December 25, 2021, the updates on James Webb’s progress have been more and more exciting.

In late January, roughly a month after launch, James Webb arrived at its destination nearly a million miles away from Earth. Not too long after arriving at its destination, the very first images from James Webb were revealed. One image showed Webb’s array of mirrors, while the other showed the star HD 84406 18 times. The star showed up 18 times as the mirror segments were not yet aligned.

Progress on the telescope continued, each dot of light was identified by the mirror segment that reflected it, and they were aligned in the hexagonal pattern of Webb’s mirrors. From there, each of the mirrors was adjusted to bring the 18 points of starlight into one in the center of the image.

At the time (the end of February), NASA was moving onto the coarse phasing of the telescope. The agency described the coarse phasing as follows:

Although Image Stacking puts all the light in one place on the detector, the segments are still acting as 18 small telescopes rather than one big one. The segments need to be lined up with each other with an accuracy smaller than the wavelength of the light.

1. Segment Image Identification
2. Segment Alignment
3. Image Stacking
4. Coarse Phasing
5. Fine Phasing
6. Telescope Alignment Over Instrument Fields of View
7. Iterate Alignment for Final Correction

Since then, in stages of alignment called “coarse phasing” and “fine phasing,” engineers have made smaller adjustments to the positions of Webb’s 18 primary mirror segments so they act as a single mirror, producing a sharp and focused image of a single star.

This coarse and fine phasing has resulted in the single, sharp image of a star the NASA just released. We can expect more information on the image, as well as the anticipated progress of James Webb moving forward, at the 12 p.m. virtual briefing NASA is giving today, March 16.