How far are the farthest things in these surveys?


@ChristineM posted a good link to an answer for this question, for the SDSS survey (which isn’t as sensitive as the Legacy Surveys):

That red smudge is probably a high-redshift galaxy; it’ll be several billions of light-years distant.

Nearby is this quasar observed with spectroscopy by SDSS; at redshift 3, it’s like 10 billion light-years distant.

By the way, “distances” for high-redshift objects are very weird, because it’s the whole universe expanding making objects seem to be moving away from each other. (And that’s a lot of the reason we talk about redshift rather than distance; also it’s the thing we actually observe.)




Thank you for the kind comment.

I’m puzzled by this one close by that doesn’t seem to register on the image, even though it has lower red-shift than the one you pointed out…

1 Like

“Zwarn = 0x5” is the warning flag… “Zwarn” means a warning from the redshift fitter, and usually anything other than zero means a dubious result. In this case, extremely dubious (there really is nothing there)!

:rofl: no chance of the machines taking over just yet then…

1 Like