First James Webb Images: Gaze at the Cosmic Areola

The Something Awful Forums > Main > General Bullshit > First James Webb Images: Gaze at the Cosmic Areola

Klyith: Aug 3, 2007; GBS Pledge Week

Good Sphere posted:

Does the James Webb go up and down in a circle because of constant corrections, or does it mostly naturally do that? I can kinda see it being able to orbit vertically like that because it's the Sun's gravity pulling it in one direction, and then the Earth's gravity pulling it in another direction.

It naturally oscillates around the center. Doing that is actually more stable, and so needs fewer correcting burns, than sitting right exactly at the center of the L point.

If you look at the main image for the wikipedia article about L points, you can see that while the centers might be "flat", they're flat like the very top of a hill or center of a saddle is flat. As soon as something drifts a tiny bit off the center they'd start "rolling downhill" and get pushed even more off center.

But that effect can also produce a kinda orbit around the center. It's constantly drifting away and being pushed back at the same time.

# ? Feb 16, 2022 00:10

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# ? May 17, 2024 02:41

Butterwagon: Mar 21, 2010; Lookit that stupid ass-hole!

I feel dumb because I thought the L2 point was unstable, but JWST is able to "orbit" it? Wouldn't any deviation from L2 make it drift further away if it's unstable?

# ? Feb 16, 2022 00:26

PIZZA.BAT: Nov 12, 2016

Butterwagon posted:

I feel dumb because I thought the L2 point was unstable, but JWST is able to "orbit" it? Wouldn't any deviation from L2 make it drift further away if it's unstable?

you're correct. it's going to have to constantly correct its orbit and will run out of fuel eventually. it's expected to last five to ten years iirc. i think the launch went exceptionally well so that may have added a few years

# ? Feb 16, 2022 03:35

Butterwagon: Mar 21, 2010; Lookit that stupid ass-hole!

PIZZA.BAT posted:

you're correct. it's going to have to constantly correct its orbit and will run out of fuel eventually. it's expected to last five to ten years iirc. i think the launch went exceptionally well so that may have added a few years

So why is it "orbit" and not "stay as close to L2 as possible at all times"?

# ? Feb 16, 2022 04:29

AHH F/UGH: May 25, 2002

Vincent Van Goatse posted:

Let's see you take a better selfie at Earth's L2.

His waistline is that big? gah dayum

# ? Feb 16, 2022 04:35

PIZZA.BAT: Nov 12, 2016

Butterwagon posted:

So why is it "orbit" and not "stay as close to L2 as possible at all times"?

because by your definition there's no such thing as an orbit at all

# ? Feb 16, 2022 04:47

Butterwagon: Mar 21, 2010; Lookit that stupid ass-hole!

PIZZA.BAT posted:

because by your definition there's no such thing as an orbit at all

...what

An orbit is stable. L2 is unstable. It's not a potential well, it's a saddle. How does an object orbit a saddle? If it goes off the wrong side of the saddle, it's never coming back. So why not stay on the tippy top?

# ? Feb 16, 2022 05:32

Klyith: Aug 3, 2007; GBS Pledge Week

Butterwagon posted:

I feel dumb because I thought the L2 point was unstable, but JWST is able to "orbit" it? Wouldn't any deviation from L2 make it drift further away if it's unstable?

If it was standing still relative to the L₂ point, yes, a deviation away from the center would be a compounding problem. But this halo orbit thing makes the deviations work against each other. When it's up, it gets pushed down; when it's left, it gets pushed right.

It's still not stable over the long term. Webb will need to make little corrections to stay in place, and when it runs out of fuel it'll drift off. But "unstable" is a relative thing.

Other Lagrangian points are permanently stable: L₄ & L₅. Those are the ones that Jupiter has collections of asteroids in. We could put something in the Earth's L₄ or L₅ point and it would stay there for-almost-ever. But they are very far away: as far away from Earth as the Earth is from the Sun. So you need an even bigger rocket to put something out there. And all that distance is sucky for high-bandwidth radio communication when you're sending lots of high-res telescope pictures.

There's been proposals to put a satellite out there watching the Sun to be an "early-warning" alarm for bad solar flare events. But TBQH if there was a giant solar flare I'm not sure what we'd really do about it even with an early warning.

"Hey everybody we need to shut down the entire world power grid today to protect it against this solar flare."
"End the blackout! No shutdown! No masks! Arr freedums!"

Butterwagon posted:

So why is it "orbit" and not "stay as close to L2 as possible at all times"?

Stay as close to L₂ at all times = balance a pen upright on your palm. Very hard because if you're a fraction off the pen starts falling over, and that means it tips over harder. Try it! (Use a pen, not a pencil with a sharp point. A pencil stabbed through your hand is cheating, that stays upright easily.)

"Orbit" around the L₂ = balance a moving bicycle. It's still not stable, a bicycle falls over without someone to help it. But there are some forces helping you out.

_{^{note: neither of these are exact analogies}}

edit:

Butterwagon posted:

An orbit is stable.

No, orbits are not always stable. Nothing in orbit around the Moon can ever be stable. If it's low, it gets moved around because the Moon's gravity is lumpy and uneven. If high, it gets too affected by the Earth.

There are several moons of planets that are eventually gonna impact or break up around their planet, ex Mars's moon Phobos and a tiny inner moons of Jupiter, or get flung out into space.

Klyith fucked around with this message at 05:52 on Feb 16, 2022

# ? Feb 16, 2022 05:41

Butterwagon: Mar 21, 2010; Lookit that stupid ass-hole!

Klyith posted:

If it was standing still relative to the L₂ point, yes, a deviation away from the center would be a compounding problem. But this halo orbit thing makes the deviations work against each other. When it's up, it gets pushed down; when it's left, it gets pushed right.
[...]

"Orbit" around the L₂ = balance a moving bicycle. It's still not stable, a bicycle falls over without someone to help it. But there are some forces helping you out.

Huh. I understand the metaphor but I don't know what the forces would be. I guess being too far ahead or above would get pulled back/down by the combined line of action of the earth and sun and vise versa? I think that makes sense. I still don't get why that's more stable in the inwards/outwards direction.

Klyith posted:

No, orbits are not always stable. Nothing in orbit around the Moon can ever be stable. If it's low, it gets moved around because the Moon's gravity is lumpy and uneven. If high, it gets too affected by the Earth.

Take your non-spherical cows and shove them, nerd.

# ? Feb 16, 2022 06:01

kazr: Jan 28, 2005

Klyith posted:

If it was standing still relative to the L₂ point, yes, a deviation away from the center would be a compounding problem. But this halo orbit thing makes the deviations work against each other. When it's up, it gets pushed down; when it's left, it gets pushed right.

It's still not stable over the long term. Webb will need to make little corrections to stay in place, and when it runs out of fuel it'll drift off. But "unstable" is a relative thing.

Other Lagrangian points are permanently stable: L₄ & L₅. Those are the ones that Jupiter has collections of asteroids in. We could put something in the Earth's L₄ or L₅ point and it would stay there for-almost-ever. But they are very far away: as far away from Earth as the Earth is from the Sun. So you need an even bigger rocket to put something out there. And all that distance is sucky for high-bandwidth radio communication when you're sending lots of high-res telescope pictures.

There's been proposals to put a satellite out there watching the Sun to be an "early-warning" alarm for bad solar flare events. But TBQH if there was a giant solar flare I'm not sure what we'd really do about it even with an early warning.

"Hey everybody we need to shut down the entire world power grid today to protect it against this solar flare."
"End the blackout! No shutdown! No masks! Arr freedums!"

Stay as close to L₂ at all times = balance a pen upright on your palm. Very hard because if you're a fraction off the pen starts falling over, and that means it tips over harder. Try it! (Use a pen, not a pencil with a sharp point. A pencil stabbed through your hand is cheating, that stays upright easily.)

"Orbit" around the L₂ = balance a moving bicycle. It's still not stable, a bicycle falls over without someone to help it. But there are some forces helping you out.

_{^{note: neither of these are exact analogies}}

edit:

No, orbits are not always stable. Nothing in orbit around the Moon can ever be stable. If it's low, it gets moved around because the Moon's gravity is lumpy and uneven. If high, it gets too affected by the Earth.

There are several moons of planets that are eventually gonna impact or break up around their planet, ex Mars's moon Phobos and a tiny inner moons of Jupiter, or get flung out into space.

Love reading this poo poo tell me more, also your avatar is incredible lol

# ? Feb 16, 2022 06:09

AHH F/UGH: May 25, 2002

this thing is so loving cool, those first photos are gonna be so loving badass

# ? Feb 16, 2022 08:04

catfry: Oct 9, 2012; by Azathoth

JWST requires corrections to its orbit but it is really limited. it's equivalent to ~10 cm/s speed change every 30 days, ~0,036 km/h delta-v.

They are not exactly at L2 because that's strictly impossible, the point changes too fast because the Earth orbit is not circular, and the earth moon system gravity perturbs it.
- Also what someone mentioned about being in the Earth shadow.
- And pointing your comms antenna at the Earth means pointing it at the sun, the largest noise generator in the solar system which really messes with your bitrate.
- Also it is more difficult to reach L2 than to reach an orbit around it. That's just how the math works out. If you are some hairy maths ape there's a bit to get you started in these slides https://sci.esa.int/documents/32965/35909/1567257599705-hp-sst-martin-hechler.pdf

# ? Feb 16, 2022 11:10

Klyith: Aug 3, 2007; GBS Pledge Week

Butterwagon posted:

Huh. I understand the metaphor but I don't know what the forces would be. I guess being too far ahead or above would get pulled back/down by the combined line of action of the earth and sun and vise versa? I think that makes sense.

Yeah. Gravity, plus centripetal forces of moving on a curved path in the "real" orbit around the Sun. It's really hard to intuitively understand, rotating reference frames are like that. And the math for this stuff is so difficult that it wasn't possible to solve until the 70s and 80s with computer simulation.

I loving hated anything to do with rotational forces back when I was in college, never quite got it. Playing Kerbal Space Program literally helped me understand this stuff in ways that a college course didn't.

Butterwagon posted:

I still don't get why that's more stable in the inwards/outwards direction.

Remember the initial explanation about how the L₂ point is the sweet spot along the line of Earth+Sun gravity. Once you're at the point with the correct speed, if you drift inwards you get more combined gravity that pulls you further in. Drifting outwards means you experience less gravity and your excess speed carries you out.

edit: I misread. How does the orbit correct for the inwards/outwards deviation?

Ok, it's like this, when you're in an orbit, a force will produce orbital motion 90� off of where the force is pointing. A force that adds speed makes you move out. One that pushes out makes you move backwards. Slowing down takes you in, and in makes you go forwards. So there's a natural cycle to that. JWST moves through each of these areas of force for just the right amount of time to change the true orbit around the Sun in ways that make a complete circle.

The halo orbit is very squashed in the in/out direction, and much wider in the x/y plane as seen from Earth. The in/out force is much steeper than the other two.

kazr posted:

Love reading this poo poo tell me more, also your avatar is incredible lol

An additional thing that makes all this harder for JWST: it can't back up.

Normally on a spacecraft you'd put little mini thrusters on all six sides. That way it can make corrections in any direction up/down, left/right, and forward/backward. The JWST has them on its boxy control module below the sunshield.

But that's a problem -- if they had thrusters firing forwards they'd fire straight into the insanely delicate sunshield and tear it up. And they can't put them above the shield because the totally exposed mirror is up there. So it can only thrust in 5 directions! That means that every maneuver they do, they're always aiming to be just a tiny bit short in that outwards direction.

It's like they're kicking a ball up a hill and never want to kick hard enough that it goes all the way over the hill and starts rolling down the other side, then you'd lose your ball.

(I like my av too, but it does have the residual shame of being purchased to support the Lowtax Spine Scam.)

Klyith fucked around with this message at 17:05 on Feb 16, 2022

# ? Feb 16, 2022 16:24

SAY YOHO: Oct 5, 2021

Thanks for all the effort posts. I don't play Kerbal, but I do play Orbiter, and can attest to learning a lot that way, space flight is incredibly complex. Even figuring out how to return from the Moon is counterintuitive at first.

# ? Feb 17, 2022 01:06

Mirage: Oct 27, 2000; All is for the best, in this, the best of all possible worlds

If it were exactly at L₂ it would be in Earth's shadow, and they need it to be somewhere the solar panel works.

L₄ or L₅ are full of enough dust and small asteroids to be dangerous.

L₃ is on the far side of the Sun, so that's out.

L₁ is on the Sunward side, so that's where you put solar observatories. We have a couple there already.

# ? Feb 17, 2022 02:18

Demon Of The Fall: May 1, 2004; Nap Ghost

So this thing is still going and has all its mirrors aligned. Still a few months until it starts actual sciency stuff, but look at the clarity of this poo poo! We�re gonna see all the aliens.

https://twitter.com/AndrasGaspar/status/1520184730985148418?s=20&t=xMO79fHp4ZHniBF5Cbcgfg

edit: MORE UPDATES

https://twitter.com/NASAWebb/status/1520096771476701184?s=20&t=MpCNIdfwwPcI-RyLgTbPkQ

Demon Of The Fall fucked around with this message at 17:49 on May 2, 2022

# ? May 2, 2022 17:42

Colonel Cancer: Sep 26, 2015; Tune into the fireplace channel, you absolute buffoon

Well did they see any aliums yet or is it more wasted money

# ? May 2, 2022 17:50

Bad Purchase: Jun 17, 2019

Demon Of The Fall posted:

https://twitter.com/AndrasGaspar/status/1520184730985148418?s=20&t=xMO79fHp4ZHniBF5Cbcgfg

so they replaced that nice creamy bokeh of the older telescopes with a bunch of harsh lens flares, and we're supposed to be impressed?

i'd be ashamed if it were my portfolio.

# ? May 2, 2022 18:02

Big Beef City: Aug 15, 2013

Klyith posted:

Yeah. Gravity, plus centripetal forces of moving on a curved path in the "real" orbit around the Sun. It's really hard to intuitively understand, rotating reference frames are like that. And the math for this stuff is so difficult that it wasn't possible to solve until the 70s and 80s with computer simulation.

I loving hated anything to do with rotational forces back when I was in college, never quite got it. Playing Kerbal Space Program literally helped me understand this stuff in ways that a college course didn't.

Remember the initial explanation about how the L₂ point is the sweet spot along the line of Earth+Sun gravity. Once you're at the point with the correct speed, if you drift inwards you get more combined gravity that pulls you further in. Drifting outwards means you experience less gravity and your excess speed carries you out.

edit: I misread. How does the orbit correct for the inwards/outwards deviation?

Ok, it's like this, when you're in an orbit, a force will produce orbital motion 90� off of where the force is pointing. A force that adds speed makes you move out. One that pushes out makes you move backwards. Slowing down takes you in, and in makes you go forwards. So there's a natural cycle to that. JWST moves through each of these areas of force for just the right amount of time to change the true orbit around the Sun in ways that make a complete circle.

The halo orbit is very squashed in the in/out direction, and much wider in the x/y plane as seen from Earth. The in/out force is much steeper than the other two.

An additional thing that makes all this harder for JWST: it can't back up.

Normally on a spacecraft you'd put little mini thrusters on all six sides. That way it can make corrections in any direction up/down, left/right, and forward/backward. The JWST has them on its boxy control module below the sunshield.

But that's a problem -- if they had thrusters firing forwards they'd fire straight into the insanely delicate sunshield and tear it up. And they can't put them above the shield because the totally exposed mirror is up there. So it can only thrust in 5 directions! That means that every maneuver they do, they're always aiming to be just a tiny bit short in that outwards direction.

It's like they're kicking a ball up a hill and never want to kick hard enough that it goes all the way over the hill and starts rolling down the other side, then you'd lose your ball.

(I like my av too, but it does have the residual shame of being purchased to support the Lowtax Spine Scam.)

Great thanks for nothing that will ever be practical.

# ? May 2, 2022 18:49

AHH F/UGH: May 25, 2002

Hell fuckin yeah baby

https://www.cnn.com/2022/06/29/world/james-webb-space-telescope-images-update-scn/index.html

# ? Jun 29, 2022 21:35

Seth Pecksniff: May 27, 2004; can't believe shrek is fucking dead. rip to a real one.

AHH F/UGH posted:

Hell fuckin yeah baby

https://www.cnn.com/2022/06/29/world/james-webb-space-telescope-images-update-scn/index.html

I can't wait!!

# ? Jun 29, 2022 21:36

AHH F/UGH: May 25, 2002

Somehow like every single one of the 160 individual parts that had to not fail to get it where it is actually didn't fail

# ? Jun 29, 2022 21:37

Songbearer: Jul 12, 2007; Fuck you say?

YOU CAN'T LAUNCH A loving TELESCOPE INTO SPACE HOW ARE WE SUPPOSED TO PEER INTO IT NOW YOU IDIOTS

# ? Jun 29, 2022 21:40

smoobles: Sep 4, 2014

Songbearer posted:

YOU CAN'T LAUNCH A loving TELESCOPE INTO SPACE HOW ARE WE SUPPOSED TO PEER INTO IT NOW YOU IDIOTS

they're gonna point another telescope at that telescope, obviously

# ? Jun 29, 2022 21:42

Strategic Tea: Sep 1, 2012

Songbearer posted:

YOU CAN'T LAUNCH A loving TELESCOPE INTO SPACE HOW ARE WE SUPPOSED TO PEER INTO IT NOW YOU IDIOTS

This is 'REAL' astronomy performed by 'REAL' scientists

They have been taking us for fools

# ? Jun 29, 2022 22:43

BAGS FLY AT NOON: Apr 6, 2011; A Soft Nylon Bag

I�m at the J-Webbs right now peeping in ur windows

# ? Jun 30, 2022 01:34

ClamdestineBoyster: Aug 15, 2015; Can't post for 10 years!

BAGS FLY AT NOON posted:

I�m at the J-Webbs right now peeping in ur windows

Show boob. :owned:

Enhance.

# ? Jun 30, 2022 01:50

Mozi: Apr 4, 2004; Forms change so fast
Time is moving past
Memory is smoke
Gonna get wider when I die; Nap Ghost

turn on your monitor

# ? Jun 30, 2022 01:51

Colonel Cancer: Sep 26, 2015; Tune into the fireplace channel, you absolute buffoon

I'm sorry to report James Webb collided with a UFO

# ? Jun 30, 2022 02:06

Seth Pecksniff: May 27, 2004; can't believe shrek is fucking dead. rip to a real one.

It can finally image a goon penis

# ? Jun 30, 2022 02:08

Colonel Cancer: Sep 26, 2015; Tune into the fireplace channel, you absolute buffoon

You're thinking of a microscope :smuggo:

# ? Jun 30, 2022 02:09

Demon Of The Fall: May 1, 2004; Nap Ghost

It�ll also have a picture of the alien bong smoke around an exoplanet

# ? Jun 30, 2022 02:30

Skeleton Ape: Dec 21, 2008

# ? Jun 30, 2022 03:27

Demon Of The Fall: May 1, 2004; Nap Ghost

5 days until NASA reveals the first images from Webb, and they are having a live broadcast which should be fun. They also released a test image that casually is the deepest view of the universe we've probably seen. I can't wait to see what this baby can really do.

https://twitter.com/NASAWebb/status/1545035473051172866?s=20&t=Qo5wO3qXauuj_WacRhswSg

https://twitter.com/NASAWebb/status/1544779918554406916?s=20&t=Qo5wO3qXauuj_WacRhswSg

# ? Jul 7, 2022 15:44