A major milestone has been achieved in the deployment of the James Webb Space Telescope, with an onboard instrument detecting its first photons from a distant star. This means engineers can now begin the three-month process of aligning the space telescope’s 18 mirrors.
After years of delays and a seemingly endless succession of hiccups during development, the $10 billion Webb mission—now in its seventh week—has been smooth as silk. The painstaking process of unfolding the space telescope and getting it ready to perform groundbreaking astronomy has been progressing about as well as anyone could’ve hoped, the most recent achievement being the telescope’s first detection of starlight, which happened earlier this week.
“This milestone marks the first of many steps to capture images that are at first unfocused and use them to slowly fine-tune the telescope,” NASA said in a statement announcing the accomplishment on Thursday. “This is the very beginning of the process, but so far the initial results match expectations and simulations.”
This inaugural
batch of photons was detected by Webb’s Near Infrared Camera (NIRCam) instrument. The photons
came from HD 84406, a star located nearly 260 light-years away and visible in
the Ursa Major constellation. With this starlight detected, the team can now
begin the three-month process of positioning all 18 panels such that they’ll
form a single concave mirror.
Launched on
December 25, 2021, the Webb space telescope is a collaboration between NASA,
ESA, and the Canadian Space Agency. Once operational, Webb will search for
light from the first stars and galaxies, study the formation and evolution of
galaxies, and scan the atmospheres of distant exoplanets, among other
astronomical and astrobiological goals.
Webb reached its
stable orbital spot, Lagrange Point 2, on January 24, 2022. Since that time,
engineers have finished powering on its science instruments and turned off its
heaters, which they did to kickstart a protracted cooling down process. The
heaters were required to keep Webb’s optics warm and to prevent the
condensation of water and ice. The alignment process was able to begin
once the instrument reached -244 degrees Fahrenheit (-153 degrees
Celsius), according to NASA.
The alignment
process will involve seven different steps, such as segment image
identification, segment alignment, and image stacking. Full details of these
steps can be found here. But as NASA explains, this job will require
extraordinary precision:
To work together
as a single mirror, the telescope’s 18 primary mirror segments need to match
each other to a fraction of a wavelength of light – approximately 50
nanometers. To put this in perspective, if the Webb primary mirror were the
size of the United States, each segment would be the size of Texas, and the
team would need to line the height of those Texas-sized segments up with each
other to an accuracy of about 1.5 inches.
Engineers will use
the data gathered by NIRCam to gradually align the telescope. As the large
mirror is not yet aligned, the incoming photons produced an image showing 18
blurry dots of light. The team will keep Webb trained on HD 84406 and work
towards producing a single focused image of the star. NASA cautions that the
images gathered throughout this three-month process will be strictly
utilitarian in nature and not “pretty,” and also a pale comparison to what we
can expect this coming summer.
The end of this
process will see a fully aligned telescope and the beginning of the next phase:
instrument commissioning. Fingers are crossed that these next important steps
will go as planned and that we’ll see spectacular results as early as June.