When the James Webb Space Telescope was launched in December. ultimately reaching the Lagrangian point L5, I noted five critical phases that had to be successfully fulfilled in order to render this $10 billion investment worth its price. They were:
- The secondary mirror, which reflects light from the main mirror to the science instruments, unfolding.
- High amplification antenna begins transmitting so Webb can communicate with Earth
- Primary mirror segments begin to open and latch in place
- At 96 days after launch, the telescope reaches its final temperature of 40 K (-233 C), i.e. for the mirrors and near infrared system to function- and just under 7K for the mid-infrared system.
- At 118 days eighteen segments align to act as one continuous honeycomb -shaped mirror - forming the full 21.5 ft. diameter instrument.
- At 180 days the calibration of science instruments will be complete.
Currently we are roughly 44 percent into completion of all phases But more than enough to establish the correct align ment of key optical elements, enabling a startling image to be taken of a star called 2MASS J17554042+6551277. Yeah, that's almost as garbled and lengthy as one of the most cockeyed passwords, ever. But it is a real star and its image is as real as the instrument that made it. Previous steps of the commissioning process - we are informed - centered on HD 84406, a star in the constellation Ursa Major that is located about 241 light-years from Earth.
What was the big deal in just obtaining one stellar image? Well, mainly to test the optics - to determine if they were in proper alignment such that the instrument was capable of gathering celestial light and delivering it to imaging instruments. All indications are that it passed with flying colors.
Let's recall, as I already noted, this monstrous primary mirror was way too big to fit inside the nose cone of any existing rocket. Hence, the mirror was built in 18 segments that had to fold together like the petals of an origami flower. You can get a better view of that mirror here:
In the nearly three months since the telescope’s Dec. 25 launch, mission scientists have been adjusting the segments so that they could produce a single, unified image. That was accomplished with the unified image of the star. Now that they have done so, mission scientists feel certain that Webb’s optics will perform as designed.
The “generic, anonymous” star seen in the image produces light that is about 100 times fainter than the human eye can see, according to Marshall Perrin, Webb’s deputy telescope scientist at the Space Telescope Science Institute in Baltimore. Let's recall every 5 increments (UNITS) difference in the stellar magnitude scale translates into 100 times difference in brightness. This is because each succeeding magnitude is different from the earlier one by 2.512 times, since:(2.515)5 = 100. Thus a star of +1 magnitude is 100 times brighter than a star of +6 magnitude on the stellar magnitude scale, since:
(6 – 1)= 5.
So if the faintest star the human eye can see is magnitude +6, that means this particular Webb -focused star would have a magnitude of +11, given it would be 100 times dimmer than the faintest star the eye can see.
I.e. +11 - 5 = +6
)--+11-----------+6---------------0--------------(-6)--------------(
----(- 5)----->
It appears reddish in the photo as the result of the use of a contrast-optimizing filter, according to NASA. This is because the infrared light captured in the image is invisible to humans.
Over the next two months, mission scientists will align Webb’s mirrors with the four instruments aboard the observatory and complete final alignment adjustments. Scientific operations are expected to begin in July, after the telescope is fully commissioned. Needless to say, those of us into astronomy or researchers, can't wait to see what new finds await!
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