3 ms·

Is there a physical limit to the resolution we can get from such absurdly large distances? And if so - is there an equation?

all2 5y ago
I vaguely recall that image resolution is a function of total photons inbound, distance to the object being observed, and effective sensor size. The photon density (assuming the source is not a point source) varies over the distance to the observed object, which will place a theoretical limit on resolution. The other half is sensor size, ie, can we catch enough photons to make sense of what's emitting/reflecting them? I haven't touched optics in a long time, though.
- andreareina 5y ago
  It's proportional to the aperture diameter and inversely proportional to the wavelength. That's why they needed telescopes that spanned the globe for that image of a black hole. More photons does get you shorter exposure times (and therefore better temporal resolution, fair enough). JWST by the way is able to resolve at this theoretical limit, which is just wild.
gizmo686 5y ago
The theoretical limit for resolution comes from diffraction. It is a function of the wavelength of light being observed, and the size of the telescope. This is measured by the Rayleigh criterion For a telescope with a circular apeture, the resolution is given by aproximatly R ~ 1.22 λ/D where: * λ is the wavelength * D is the diameter * 1.22 is the first zero of the intensity function for the Airy Disk
astroH 5y ago
A lot of the work on distant galaxies is not being done with gravitational lensing. The idea is that you use massive objects in the foreground, like galaxy clusters, to focus light from the background. Depending on orientation, we can get magnifications of more than 10,000. There was a recent press release of such an example. So in principle, our telescopes combined with gravitational lenses can resolve almost all of the relevant detail we would want of a galaxy if the orientation is correct. It rarely is of course but there are a few examples so such strong lenses.

all2 5y ago

I vaguely recall that image resolution is a function of total photons inbound, distance to the object being observed, and effective sensor size. The photon density (assuming the source is not a point source) varies over the distance to the observed object, which will place a theoretical limit on resolution. The other half is sensor size, ie, can we catch enough photons to make sense of what's emitting/reflecting them? I haven't touched optics in a long time, though.

andreareina 5y ago
It's proportional to the aperture diameter and inversely proportional to the wavelength. That's why they needed telescopes that spanned the globe for that image of a black hole. More photons does get you shorter exposure times (and therefore better temporal resolution, fair enough). JWST by the way is able to resolve at this theoretical limit, which is just wild.

gizmo686 5y ago

The theoretical limit for resolution comes from diffraction. It is a function of the wavelength of light being observed, and the size of the telescope. This is measured by the Rayleigh criterion For a telescope with a circular apeture, the resolution is given by aproximatly R ~ 1.22 λ/D where: * λ is the wavelength * D is the diameter * 1.22 is the first zero of the intensity function for the Airy Disk

astroH 5y ago

A lot of the work on distant galaxies is not being done with gravitational lensing. The idea is that you use massive objects in the foreground, like galaxy clusters, to focus light from the background. Depending on orientation, we can get magnifications of more than 10,000. There was a recent press release of such an example. So in principle, our telescopes combined with gravitational lenses can resolve almost all of the relevant detail we would want of a galaxy if the orientation is correct. It rarely is of course but there are a few examples so such strong lenses.