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March 29, 2024, 11:26:31 AM

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James Webb Space Telescope

Started by Alberon, December 24, 2021, 12:17:20 AM

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Butchers Blind

Quote from: Alberon on January 24, 2022, 08:34:40 PMOnly four months until we start getting photos!

Bit like Boots in the old days.

imitationleather

Quote from: Butchers Blind on January 24, 2022, 09:54:57 PMBit like Boots in the old days.

Hope they don't come back with those Quality Control stickers on them!!

MojoJojo

Quote from: Milo on January 24, 2022, 08:57:54 PMI still can't get my head around how its orbit works.

I found this line from NASA helpful (https://webb.nasa.gov/content/about/orbit.html)
QuoteIf Webb is orbiting the Sun further out than Earth, shouldn't it take more than a year to orbit the Sun? Normally yes, but the balance of the combined gravitational pull of the Sun and the Earth at the L2 point means that Webb will keep up with the Earth as it goes around the Sun.

It's further out, so the normal stable orbit would take more than a year. But because it is lined up with earth, there is a greater gravitational pull, that means its stable orbit is faster. The L2 point is where the speed up from being aligned with earth makes it take exactly a year to orbit the sun, so it stays aligned with the earth and it stays stable.

Closer to the earth it would overtake the earth, lose the gravity attraction from the earth and then fly off into space. Further away it would fall behind the earth and the same thing would happen again.

Mr_Simnock

Quote from: MojoJojo on January 25, 2022, 11:29:08 AMCloser to the earth it would overtake the earth, lose the gravity attraction from the earth and then fly off into space. Further away it would fall behind the earth and the same thing would happen again.

The spacecraft has been positioned so that it will always gently fall back towards earth. It has correctional thrusters only on the underside facing the earth\sun so they can't correct if it crosses the point where it will only drift further away.

touchingcloth

Quote from: MojoJojo on January 25, 2022, 11:29:08 AMI found this line from NASA helpful (https://webb.nasa.gov/content/about/orbit.html)
It's further out, so the normal stable orbit would take more than a year. But because it is lined up with earth, there is a greater gravitational pull, that means its stable orbit is faster. The L2 point is where the speed up from being aligned with earth makes it take exactly a year to orbit the sun, so it stays aligned with the earth and it stays stable.

Closer to the earth it would overtake the earth, lose the gravity attraction from the earth and then fly off into space. Further away it would fall behind the earth and the same thing would happen again.

That describes how the Lagrange points themselves work, but the JWST isn't sitting still in that point but will be orbiting around it, which is a bit of orbital mechanical madness I don't have the imagination or maths skills to get my head around. I thought three body problems were when the missus caught me in bed with that tart!!

Alberon

I must admit I don't really know myself, but a quick google says that the L1, L2 and L3 points are metastable. That means that if you put something there it will drift away in time. Rather than at L4 and L5 where if you put something there it will stay there.



Apparently this orbit around L2 is roughly to scale in this diagram and takes six months to complete. I'm guessing that a course correction sends it back around twice a year.

Replies From View

Bored with this telescope now.  New one please.

Alberon

They're building a new one now with snapchat filters built in. It'll cost $500 billion and it'll be ready in 2056.

Butchers Blind

My uncle's got a telescope in his back garden, doesn't make a big fuss about it like this lot. Has it pointed at the bathroom window of the house four doors down, great views.

robhug

Quote from: Butchers Blind on January 26, 2022, 10:34:36 AMMy uncle's got a telescope in his back garden, doesn't make a big fuss about it like this lot. Has it pointed at the bathroom window of the house four doors down, great views.

She'd never have caught that thrush flaring up again if he hadn't tipped her off.

mothman

Quote from: Mr_Simnock on January 25, 2022, 12:08:01 PMThe spacecraft has been positioned so that it will always gently fall back towards earth.
Well of course. How else would they get the film back for developing?

Keebleman

If all this space stuff leads you needing a fix of extreme cosmology, then you might be interested in this.  It's a magnificent course, via Wondrium (formerly The Great Courses), comprising 12 half-hour lectures about the first 0.0000000000001 (or so) seconds of the universe, with occasional speculation about what things will look like in 1,000,000,000,000,000,000,000 (or so) years time.  The professor looks and sounds rather like Emo Phillips, so rather offputting at first but it's remarkable how quickly he wins you over. And his command of the material is superb.  He tells us not just what we know, but how we came to know it.

https://www.wondrium.com/the-big-bang-and-beyond-exploring-the-early-universe

Tone is so hard to get right with these things, but this guy manages it: he is never patronising or too obscure, and attempts at humour are very rare and, remarkably, often successful.  You can tell he has never lost the awe and wonder that must first have drawn him to the topic.

Alberon

The first photo from the James Webb has been released, but don't expect too much to begin with.



Great, huh?

Actually all the stars in that composite image are actually the same star. This shows which segment is responsible for each image.



The calibration process will eventually have each hexagonal segment combining the image into one. This star is HD 84406 was chosen for it's isolated brightness. I've read elsewhere that when callibration is complete it will be too bright for the telescope to look at.

Replies From View

More detail is coming through...




Aaargh!

NoSleep

The main imaging detector has been aligned today.


Fr.Bigley

But can it see into the future. The past is boooooooooooooooring

TrenterPercenter

Quote from: NoSleep on March 16, 2022, 05:51:26 PMThe main imaging detector has been aligned today.

Why does every public facing theoretical/astro/physicist/mathematician (Al-Khalil aside) have to come across as such hyperactive bellends?



Btw I know the answer "enthusiasm for the weens".  You heard me.

touchingcloth

Quote from: TrenterPercenter on March 16, 2022, 06:02:43 PMWhy does every public facing theoretical/astro/physicist/mathematician (Al-Khalil aside) have to come across as such hyperactive bellends?

Btw I know the answer "enthusiasm for the weens".  You heard me.

If they found being gregarious and enthusiastic easy and wanted to make money out of it they'd turn to advertising or something.

It's a little unfair to criticise scientists for not being able excellent public communicators first and passable scientists second. For what it's worth, I didn't get a "hyperactive bellend" vibe from that video.

NoSleep

Quote from: TrenterPercenter on March 16, 2022, 06:02:43 PMWhy does every public facing theoretical/astro/physicist/mathematician (Al-Khalil aside) have to come across as such hyperactive bellends?

Longing for the good old days when astronomy presenters were more sober and serious? Like Patrick Moore?

TrenterPercenter

Quote from: touchingcloth on March 16, 2022, 06:50:12 PMIf they found being gregarious and enthusiastic easy and wanted to make money out of it they'd turn to advertising or something.

It's a little unfair to criticise scientists for not being able excellent public communicators first and passable scientists second. For what it's worth, I didn't get a "hyperactive bellend" vibe from that video.

Well you know variety is the spice of life.

Its nothing to do with being "passable scientists" it is a stylist decision, you might not find people's faux-laughter at their own amazeballs comments annoying.  I do.

And that is fine.

TrenterPercenter

Quote from: NoSleep on March 16, 2022, 07:25:40 PMLonging for the good old days when astronomy presenters were more sober and serious? Like Patrick Moore?

Now we're talkin'


Replies From View

If you can't easily imagine them advertising Kinder Eggs, then they are simply not scientists.

Replies From View

Anyway, enough of this, when is the next space telescope due to be released?

Anyone noticed all the clickbait shite on Youtube about the JWT? Lots of videos showing stunning pics of galaxies, etc that are supposed to have been taken by the JWT when it hasn't even got its optics aligned yet. And all the videos have 'comments are turned off' so you can't tell them what a bunch of lying bastards they are.

The Dog

Quote from: Replies From View on March 16, 2022, 08:50:48 PMIf you can't easily imagine them advertising Kinder Eggs, then they are simply not scientists.

Quote from: Albert EinsteinI have always depended on the kindness of eggs


It's just sent its very first star image and it's wonderful. The star (in Ursa Major) is slightly below naked eye visibility, but it's still so bright that it has six great long streaks coming out of it, showing that it's just too bright a star for such a huge mirror to cope with.

I've just seen a Youtube video that talks about the resolution they're getting from it: less than a tenth of an arc second (the diameter of the full oon is around 108,000 arcseconds.

Did you know that the motors aligning its mirrors can move slower than a blade of grass growing/ We live in truly wonderful times.

Replies From View

Quote from: J Peasemould Gruntfuttock on March 16, 2022, 09:36:51 PMDid you know that the motors aligning its mirrors can move slower than a blade of grass growing

Bet it gets picked on at school.

Video Game Fan 2000

Quote from: TrenterPercenter on March 16, 2022, 08:32:37 PMNow we're talkin'



I put the konami code into the James Webb Space Telescope and now I can see Lara Croft with her skanties off

and I'll kill myself before I set it back to normal, sorry boffins

Blumf

Quote from: J Peasemould Gruntfuttock on March 16, 2022, 09:36:51 PMDid you know that the motors aligning its mirrors can move slower than a blade of grass growing/ We live in truly wonderful times.

The mirror actuators are a neat design:
https://www.youtube.com/watch?v=5MxH1sfJLBQ

2cm of coarse range with less than 1μm step size, and fine range is 10μm with less than 8nm step. All from a single drive motor!

Replies From View

So will it manage 10,000 steps a day or can we expect it to be a fat fuck by November.