The James Webb Telescope captured this stunning image of a Milky Way star, 2MASS J17554042+6551277, along with distant galaxies in the background. (Image Credit: NASA/STScl)
On March 16th, the James Webb Telescope transmitted its most detailed image back to NASA, a striking view of the glimmering orange 2MASS J17554042+6551277 star that lies approximately 2,000 light-years away. A red filter was used in the process, making the star stand out more in the surrounding blackness with galaxies and distant stars glimmering in the background. The results demonstrate that the telescope's 18 individual mirrors are correctly aligned and can now work as one mirror.
NASA said that the fine phasing mirror alignments stage indicates that the optical parameters are checked to confirm the telescope can collect light from other distant objects. "You not only see the star and the spikes from the diffraction of the star, but you see other stars in the field that are tightly focused, just like we expect, and all sorts of other interesting structures in the background," Webb engineer Lee Feinberg said at the NASA news conference. "We've actually done a very detailed analysis of the images we're getting, and so far, what we're finding is that the performance is as good [as], if not better than, our most optimistic prediction." Feinberg led the alignment project so that the telescope's 18 hexagonal beryllium mirrors can operate as one mirror measuring 21.3 feet in diameter.
Scientists also said the sharp image focus occurred due to the mirrors adjusting to within a few nanometers. "We now have achieved what's called 'diffraction-limited alignment' of the telescope," Marshall Perrin, Webb deputy scientist at the Space Telescope Science Institute in Baltimore, said. "The images are focused together as finely as the laws of physics allow."
Last month, Webb released a photograph that showed 18 images of a star in a hexagonal arrangement. The images came from each of the telescope's mirrors, which were aligned to face the same direction.
A central image is produced when light travels through a lens. Afterward, a circle of diffraction rings surrounds the image. The wavelength-based diffraction limit, lens power, and distance from the measured object play a key role in determining the proximity of two objects before a perfect lens can no longer tell them apart. So far, the most recent test photograph outperforms Hubble's capabilities.
"The engineering images that we see today are as sharp and as crisp as the images that Hubble can take but are at a wavelength of light that is totally invisible to Hubble," said Jane Rigby, operations project scientist for Webb at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "So this is making the invisible universe snap into very, very sharp focus."
Hubble collects and focuses light via two mirrors in a Cassegrain telescope design. The light moves down the telescope before reaching the concave, primary mirror. Afterward, this light bounces off the primary mirror and moves toward the telescope's frontal region. It then hits the convex-shaped secondary mirror, which concentrates the light into a beam that travels through the primary mirror's hole. This light is then analyzed by science and guidance instruments.
The next process, taking six weeks to complete, involves refining the alignment and powering up most of the instruments on Webb. That includes the Near-Infrared Spectrograph, which observes the light spectra from distant objects to understand their chemical and temperature composition. Another instrument the team will bring online is the Mid-Infrared Instrument, which serves as a camera and spectrograph to capture images in wavelengths not seen by the human eye. Lastly, the team plans to power up the Near-Infrared Imager and Slitless Spectrograph, a powerful instrument that explores and observes orbiting exoplanets. Afterward, the Webb team plans to correct the mirrors' position errors via necessary adjustments.
Overall, the telescope's optical system is expected to be completed by May. Then, the instruments undergo further preparations for two months. Based on that timeline, the telescope could start producing full-resolution images and data by the summer.
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