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: Hubble isn't as sensitive in the infrared as Webb. A lot of the stars and structure Webb has revealed in the two nebulae especially is due to it picking up a lot more of the infrared light to which the gas and dust of the nebulae are essentially transparent. In other words the data is qualitatively different in addition to the increased resolution. 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.
As for the quantitative part, I guess mirror size is what you'd want to look at? Hubble has a single circular primary mirror with a diameter of 2.4 metres.[0]
Webb has 18 hexagonal mirror segments that are combined into the equivalent of a circular mirror with diameter 6.5m. That is ~6.25 times the light collection area of Hubble(25.4m² vs 4m²)[1]
> That is ~6.25 times the light collection area of Hubble(25.4m² vs 4m²)
This would have to be scaled by the wavelength being observed, for a resolution comparison. Hubble actually has better absolute resolution, when viewing shorter the wavelengths that JWT can't sense (0.05 arcseconds vs JWT 0.1 arcseconds).
Right, that didn't occur to me at first, but is just obviously true when you point it out, thanks. Though I didn't know that hubble is actually higher resolution in that comparison.
Then, in some sense, the first part of my explanation is most of the story in the case of comparing MIRI(mid-infrared instrument) to hubble in the near-infrared.
But in comparing NIRCAM to Hubble in the near-infraread JWST would in fact have greater resolution, no?
Plus, upgrading Hubble wouldn't get us close either. JWST is specifically designed to shield the sensors from IR/heat, and it's 1 million miles from Earth for a similar reason.
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.
>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: Hubble isn't as sensitive in the infrared as Webb. A lot of the stars and structure Webb has revealed in the two nebulae especially is due to it picking up a lot more of the infrared light to which the gas and dust of the nebulae are essentially transparent. In other words the data is qualitatively different in addition to the increased resolution. 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.
As for the quantitative part, I guess mirror size is what you'd want to look at? Hubble has a single circular primary mirror with a diameter of 2.4 metres.[0]
Webb has 18 hexagonal mirror segments that are combined into the equivalent of a circular mirror with diameter 6.5m. That is ~6.25 times the light collection area of Hubble(25.4m² vs 4m²)[1]
0: https://en.wikipedia.org/wiki/Hubble_Space_Telescope
1: https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Fea...