How do astronomers find the oldest sections of the sky to look at?

Question

Obviously a lot of space related questions with the JWST doing it's thing, but i wanted to know how they find the ancient sections of space to analyze? Do they scan the entirety of space looking for super redshifted space, or are there areas of the sky that are known to be particularly old?

dredmorbius · Accepted Answer

"Young" sections of the sky are near. They typically have bright stuff in them --- stars within our own galaxies, bright nearby galaxies otherwise.
In general, any part of the sky in which there are known objects ... is likely younger than parts in which there are none.
Because of the dynamics of the Big Bang, that is, the fact that the known universe was compressed to a singularity of infinite density, if you look back far enough, you'll find something, if only the cosmic background. To date, the background of every deep field image take has had fainter and remoter background objects.
Aim away from the galactic plane and away from the galactic centre. Look away from known galaxies and galactic clusters. Those are the emptiest parts of the sky, and anything you can see there will likely be both distant and old. Look for a long time (use long exposures) to gather as much light as possible. Those are deep fields, and that is old space.
You can also choose your observation frequency/wavelength based on the anticipated redshift, which itself is a function of distance.
TL;DR: Find the emptyiest part of the sky you can, and stare at it for as long as you can, at the right red for the distance.
https://en.wikipedia.org/wiki/List_of_deep_fields
Disclaimer: Though I've looked through a few 'scopes and blew up a planet once, I'm no astronomer.

potamic · Answer

Not an expert. My layman understanding is that we are at the center of the observable universe. There are no sections of the sky that are older than others. I think what the deep field image shows is that, no matter where we look we are surrounded by ancient galaxies going as far back in space and time as we are able to.

mytailorisrich · Answer

I don't think that there is any section older than any other section. It's rather a question of looking 'far' enough, which probably means targeting a very narrow section to detect very faint, 'reddish' signal.

drdeca · Answer

I think one just, looks at the parts that look emptier, so that there is less nearby stuff to get in the way of seeing the stuff further away (and this from a longer time ago)