# James Webb Space Telescope general discussion thread **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Tags:** science-math\ **Created:** [December 25, 2021, 1:18pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624 "2021-12-25T13:18:56Z")\ **Posts on this page:** 20\ **Page:** 25
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [February 26, 2022, 7:06am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/481 "2022-02-26T07:06:43Z")
> [@Senegoid](#): > > That’s impressive that they will be able to line them all up with greater resolution than one wave length. I guess it helps that they are looking at infra-red and not ultraviolet. It also sees the red part of the visible spectrum. That’s 6-700 nanometers. ---
**Author:** ![Borborygmi](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/borborygmi/32/217_2.png) [@Borborygmi](https://boards.straightdope.com/u/Borborygmi)\ **Post date:** [February 26, 2022, 1:47pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/482 "2022-02-26T13:47:11Z")
> [@Senegoid](#): > > That’s impressive that they will be able to line them all up with greater resolution than one wave length. I guess it helps that they are looking at infra-red and not ultraviolet. Pffft. Always taking the easy way out, these guys. ---
**Author:** ![pjd](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pjd/32/3009_2.png) [@pjd](https://boards.straightdope.com/u/pjd)\ **Post date:** [March 4, 2022, 9:12pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/483 "2022-03-04T21:12:08Z")
Why is the MIRI device - which has to be coldest (\<7K) - more than twice as ‘hot’ as the other instruments ? What’s that all about ? ---
**Author:** ![Gorsnak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gorsnak/32/7587_2.png) [@Gorsnak](https://boards.straightdope.com/u/Gorsnak)\ **Post date:** [March 4, 2022, 9:23pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/484 "2022-03-04T21:23:26Z")
I would imagine that it has to do with its active cooling system. Either it’s slower to cool down, or they’re intentionally bringing it down slowly for reasons. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [March 5, 2022, 6:55am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/485 "2022-03-05T06:55:07Z")
> [@Gorsnak](#): > > I would imagine that it has to do with its active cooling system. Either it’s slower to cool down, or they’re intentionally bringing it down slowly for reasons.   IIRC I read that they are cooling things down very slowly. I think it’s to prevent things getting warped. The mirrors and I suppose all the other optical parts have to be aligned to micron-level precision, so even the slightest warping is too much. ---
**Author:** ![N9IWP](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/n9iwp/32/3154_2.png) [@N9IWP](https://boards.straightdope.com/u/N9IWP)\ **Post date:** [March 16, 2022, 5:45pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/486 "2022-03-16T17:45:39Z")
Alignment reached! [https://www.nasa.gov/press-release/nasa-s-webb-reaches-alignment-milestone-optics-working-successfully](https://www.nasa.gov/press-release/nasa-s-webb-reaches-alignment-milestone-optics-working-successfully) Dr Becky reacts: [![](https://img.youtube.com/vi/1nOX66G5q9E/maxresdefault.jpg "LIVE | The James Webb Space Telescope mirrors are aligned!") ](https://www.youtube.com/watch?v=1nOX66G5q9E) Brian ---
**Author:** ![kwintenstraler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kwintenstraler/32/10698_2.png) [@kwintenstraler](https://boards.straightdope.com/u/kwintenstraler)\ **Post date:** [March 16, 2022, 6:19pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/487 "2022-03-16T18:19:45Z")
Nice to read / watch ---
**Author:** ![Cardigan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cardigan/32/187_2.png) [@Cardigan](https://boards.straightdope.com/u/Cardigan)\ **Post date:** [March 16, 2022, 6:27pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/488 "2022-03-16T18:27:21Z")
I always love Dr. Becky’s enthusiasm. This is some much welcomed good news during an otherwise dark period news-wise. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [March 17, 2022, 10:06pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/489 "2022-03-17T22:06:54Z")
I imagine that there’s still a lot of fine-tuning to do. ---
**Author:** ![pjd](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pjd/32/3009_2.png) [@pjd](https://boards.straightdope.com/u/pjd)\ **Post date:** [March 17, 2022, 11:24pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/490 "2022-03-17T23:24:07Z")
There’s still a lot of cooling to do too ! ---
**Author:** ![Cardigan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cardigan/32/187_2.png) [@Cardigan](https://boards.straightdope.com/u/Cardigan)\ **Post date:** [March 18, 2022, 3:04pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/491 "2022-03-18T15:04:49Z")
I think heard JWST should be cool enough to be fully operational sometime in June. ---
**Author:** ![Gorsnak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gorsnak/32/7587_2.png) [@Gorsnak](https://boards.straightdope.com/u/Gorsnak)\ **Post date:** [March 18, 2022, 3:16pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/492 "2022-03-18T15:16:29Z")
I believe the only thing not at operational temperature is MIRI (Mid-Infrared Instrument), which is to be actively cooled down to 10K or something crazy. It’s currently at 96K and has been coming down a degree or two per day, presumably in a controlled fashion making use of the active cooling system. The mirror and other instruments are all sitting at their operating temp of around 40K and have been for weeks already. ---
**Author:** ![Skywatcher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skywatcher/32/254_2.png) [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)\ **Post date:** [March 18, 2022, 5:33pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/493 "2022-03-18T17:33:03Z")
> **[James Webb snaps first in-focus image – and photobombs another spacecraft](https://newatlas.com/space/james-webb-space-telescope-first-image-focus/)** > > The James Webb Space Telescope has snapped its first in-focus image. The milestone comes after the mission team spent the last few weeks aligning its mirrors, and the telescope is now set to meet or even exceed its original science goals. It was also... ---
**Author:** ![Fiendish\_Astronaut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiendish_astronaut/32/3295_2.png) [@Fiendish\_Astronaut](https://boards.straightdope.com/u/Fiendish_Astronaut)\ **Post date:** [March 18, 2022, 5:36pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/494 "2022-03-18T17:36:35Z")
The other spacecraft is also using that Lagrange point but apparently it’s a million miles away from the JWT. I know they orbit around the Lagrange point but are the orbits really that big? ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [March 18, 2022, 5:55pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/495 "2022-03-18T17:55:45Z")
A million km, not miles. But yes, the Lagrange orbits are huge. JWST will take about 6 months to complete a full orbit. ---
**Author:** ![Fiendish\_Astronaut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiendish_astronaut/32/3295_2.png) [@Fiendish\_Astronaut](https://boards.straightdope.com/u/Fiendish_Astronaut)\ **Post date:** [March 18, 2022, 6:06pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/496 "2022-03-18T18:06:34Z")
Thanks. I cannot wait to see what this telescope produces. To hear it’s performing above the expected parameters is wonderful. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [March 19, 2022, 7:17am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/497 "2022-03-19T07:17:30Z")
> [@Skywatcher](#): > > [James Webb snaps first in-focus image – and photobombs another spacecraft](https://newatlas.com/space/james-webb-space-telescope-first-image-focus/) That’s some major lens flare in that pic. Is this how it’s gonna be? ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [March 19, 2022, 7:38am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/498 "2022-03-19T07:38:43Z")
> [@Senegoid](#): > > Is this how it’s gonna be? Yes. It’s not lens flare, though–those are diffraction spikes, where light bends around sharp edges in the light path and bleeds elsewhere. In this case, light is bending off of the edges of the hexagonal mirror segments and the struts holding the secondary mirror in place. You can see two sets of spikes. The bright ones with 6-fold symmetry are from the mirror segments and two of the struts (which are at a 60 degree relative angle). There is also a dimmer spike with 2-way symmetry, which is from the final strut (angled halfway between the other two struts, giving a 150-150-60 degree pattern). The spikes are only apparent on very bright stars over long exposures (bright being a relative term–the one here isn’t visible to the naked eye). They’re expected and not a big deal in terms of the science. They might occasionally have to align things so that spikes from a star that they aren’t studying don’t overlap with one they are studying, but that’s all doable. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [March 19, 2022, 10:29am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/499 "2022-03-19T10:29:12Z")
Also interesting is that some of the brighter stars appear as classical pointed “star” shapes, except with six points instead of the typical five, again I’m sure due to the mirror shape. For instance there’s one about halfway down and just to the right of the vertical spike coming down from the bright star, but if you look carefully there are many others. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [March 20, 2022, 9:42am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/500 "2022-03-20T09:42:31Z")
All of the objects give off the spikes; it’s just that most are too dim to see. You can imagine that the spikes are, say, 1/1000 the brightness of the star that produces them. But that’s 1/1000 of the actual brightness, not the clamped pixel value. Two overexposed pixels will look the same, but if one is overexposed by 1000x and the other by 2x, you’re only going to notice the spikes on the former. Galaxies add another factor. Whereas stars are point sources, galaxies are smudged out, so their spikes will be even less visible for the same overall light output. There’s actually quite a lot more detail in the spikes than just the 6-fold symmetry. You could nearly reverse engineer the entire lightpath just by looking at them in detail. For instance, I suspect that the variation in the horizontal (2-fold) spikes is from the hinge and other protrusions in the top strut. [Previous page](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624.md?page=24) [Next page](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624.md?page=26)