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Compare Webb's Images to Hubble

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Re: Compare Webb's Images to Hubble

#181

Post by jekdoce »

gcbirzan wrote: post #176
mtlmtlmtlmtl wrote: post #47

Earlier quoted context omitted.

IANA{astrophysicist, space engineer} but I do follow this closely and have what I call a working armchair understanding of this stuff. Anyone from relevant fields is welcome to gently correct any imprecisions. I always want to learn more and will thank you for it >could Hubble achieve the same quality of images as Webb if it was given 100x (or whatever) more time exposure? No, for a different and simpler reason: Hubb…

> This also will see much older light which is redshifted(the longer the travel, the greater the shift) out of Hubble's range of sensitivity. It's a matter of speed not distance, isn't it?

As I understand it redshifting is due to the doppler effect, whose formula only depends on the relative speed between the observer and the sender.

However, it also seems like due to galaxies further away having a larger expansion speed, typically they are more redshifted.

Re: Compare Webb's Images to Hubble

#182

Post by Cthulhu_ »

supernova87a wrote: post #61

For the professional (or former professional) astronomers among us, I will make my somewhat amused observation that what people are most paying attention to is not really the distinguishing features of JWST. People seem most impressed by the apparent increase in resolution of the images, which is not from a certain point of view the hardest thing to do . HST might have done that if its instruments had been of differe…

If I may get political here (nothing personal / no direct reply to the parent comment):

> stunning images was enough to get the public to support a $10B project.

I don't believe public support is relevant; is there public support for the >$700B a year spent on the military?

Re: Compare Webb's Images to Hubble

#183

Post by TulliusCicero »

Cthulhu_ wrote: post #182
supernova87a wrote: post #61

For the professional (or former professional) astronomers among us, I will make my somewhat amused observation that what people are most paying attention to is not really the distinguishing features of JWST. People seem most impressed by the apparent increase in resolution of the images, which is not from a certain point of view the hardest thing to do . HST might have done that if its instruments had been of differe…

If I may get political here (nothing personal / no direct reply to the parent comment): > stunning images was enough to get the public to support a $10B project. I don't believe public support is relevant; is there public support for the >$700B a year spent on the military?

Yeah, more or less. People gripe about it occasionally, especially on the left, but then some shit will go down like Ukraine and suddenly nobody wants to look like an idiot (which will absolutely happen in an American context if you suggest cutting military spending right after Russia invades someone).

Re: Compare Webb's Images to Hubble

#184

Post by [deleted] »

rkagerer wrote: post #174
soulofmischief wrote: post #135

Earlier quoted context omitted.

It's all IR. It's color-mapped over RGB, but the sensors are IR.

Didn't the observed light shift into IR wavelengths due to the expansion of space over the last billions of years while it traveled to us? Do the recolored images have any relation to what the original view would have looked like, or is it just arbitrary "artistic license"?

[deleted]

Re: Compare Webb's Images to Hubble

#185

Post by jhugo »

rkagerer wrote: post #174
soulofmischief wrote: post #135

Earlier quoted context omitted.

It's all IR. It's color-mapped over RGB, but the sensors are IR.

Didn't the observed light shift into IR wavelengths due to the expansion of space over the last billions of years while it traveled to us? Do the recolored images have any relation to what the original view would have looked like, or is it just arbitrary "artistic license"?

Looked like from what perspective? A human eye on Earth?

Re: Compare Webb's Images to Hubble

#186

Post by gliptic »

supernova87a wrote: post #61

For the professional (or former professional) astronomers among us, I will make my somewhat amused observation that what people are most paying attention to is not really the distinguishing features of JWST. People seem most impressed by the apparent increase in resolution of the images, which is not from a certain point of view the hardest thing to do . HST might have done that if its instruments had been of differe…

> HST might have done that if its instruments had been of different pixel size or imaging array size / focal length

HST is already imaging at diffraction-limited resolution (with proper post-processing). It would need a bigger mirror to get there.

Re: Compare Webb's Images to Hubble

#187

Post by nabla9 »

supernova87a wrote: post #61

For the professional (or former professional) astronomers among us, I will make my somewhat amused observation that what people are most paying attention to is not really the distinguishing features of JWST. People seem most impressed by the apparent increase in resolution of the images, which is not from a certain point of view the hardest thing to do . HST might have done that if its instruments had been of differe…

>The new thing is observations in the IR,

Not a new thing.

Herschel space observatory operated in same location (L2-point) as JWST and it was IR telescope. https://www.google.com/search?q=Herschel+space+observatory+i...

Mirror sizes:

   Hubble    4.0 m2 (43 sq ft)
   Herschel  9.6 m2 (103 sq ft)
   JWST     25.4 m2 (273 sq ft)
Hubble had ~40% of the Herschel's collecting area and Herchel had 40% of the JWST's collecting area.

Re: Compare Webb's Images to Hubble

#188

Post by mpcjanssen »

gcbirzan wrote: post #176
mtlmtlmtlmtl wrote: post #47

Earlier quoted context omitted.

IANA{astrophysicist, space engineer} but I do follow this closely and have what I call a working armchair understanding of this stuff. Anyone from relevant fields is welcome to gently correct any imprecisions. I always want to learn more and will thank you for it >could Hubble achieve the same quality of images as Webb if it was given 100x (or whatever) more time exposure? No, for a different and simpler reason: Hubb…

> This also will see much older light which is redshifted(the longer the travel, the greater the shift) out of Hubble's range of sensitivity. It's a matter of speed not distance, isn't it?

Redshift is indeed a matter of speed. But due to the expansion of the universe, relative speed and distance are directly related (Hubble's law).

So farther away means faster relative speed and thus more redshifted (Doppler effect) Farther away also means older light (due to the finite speed of light).

Putting that all together means that to observe old light from the start of the universe we have to look in the IR spectrum.

Re: Compare Webb's Images to Hubble

#189

Post by arjvik »

jhugo wrote: post #185
rkagerer wrote: post #174

Earlier quoted context omitted.

Didn't the observed light shift into IR wavelengths due to the expansion of space over the last billions of years while it traveled to us? Do the recolored images have any relation to what the original view would have looked like, or is it just arbitrary "artistic license"?

Looked like from what perspective? A human eye on Earth?

OP clearly means from an observer moving at (approximately) the same velocity as the object emitting the light.

Re: Compare Webb's Images to Hubble

#190

Post by 5350-uiop-1130 »

old and new images already looked highly processed, that photoshop look - which i think some of us got a little jaded on maybe.

what's more interesting to me is what we can learn about exoplanets from this mission

https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-...

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