If you look in the top-left corner you'll see a bunch of controls.
The first one (with three layers) chooses what is displayed. You can choose from loads of surveys (some which cover the whole sky, others that only cover a part) at loads of different wavelengths (and because the sky does change, search for LSST, there's an implicit time aspect as well). These are the original images (ignoring the underlying reduction process each survey does), these are for science not outreach. This is the button to play with (see how the same spot looks in visible vs. radio vs. x-ray).
Next button allows you to pick specific observations (as the all-sky part has implications about how you tessellate images), not that useful unless you understand what you're doing in more details than I have space for.
After that is catalogues of objects. This information will be compiled by survey teams, and is derived from various sources (including other catalogues). The magical astronomy keyword here is "TAP" for Table Access Protocol.
Spectra and timeseries is the next button, you're (generally) looking at spectra/timeseries from individual objects here, but things get more complex here.
The remaining buttons are really of no interest outside the profession sphere (though the multi-messager (i.e. not light, think gravitational waves/neutrinos etc.) button might be interesting when LIGO is running).
(I'm an astronomy RSE, but I don't work on esasky, nor for ESA).
Now, if they had the database with hundreds of terabytes of objects that NASA has for their OpenUniverse simulation they’re running for the upcoming Roman space telescope (see https://www.jpl.nasa.gov/news/nasas-roman-mission-gets-cosmi...), then maybe I could understand why it is so confusing.
As it is, I don’t really understand why it has to be so confusing.
And using a viewpoint of a large sphere from the outside just seems wrong. It should be viewed from the inside.
There's an excellent web version of Stellarium, if anyone's interested: https://stellarium-web.org/
Also, are these [0] artefacts a result of adaptive optics since they shine out those lasers to keep track of distortions? And these [1] which seem to be the same but larger and less focused. I remember seeing similar ones on Google Sky years back but never really figured out what causes it.
[0] https://sky.esa.int/esasky/?target=94.25875681534997%2020.97...
[1] https://sky.esa.int/esasky/?target=218.7659069213465%20-59.6...
Anyhow, whoever can actually answer will surely know which ones I mean.
https://sites.astro.caltech.edu/palomar/about/telescopes/ima...
many more that i didnt list.
[1] https://www.joycenho.com/wp-content/uploads/2015/04/EXP-Stil...
If you want to explore how space changes over time, I recommend you look into something like Celestia[0]. It allows you to simulate star movement over thousands of years, and show you how the night sky looked to the Ancient Egyptians.
Nearest star to us, over time: https://commons.wikimedia.org/wiki/File:NearSunStarsSimple.j...
Star closest to the north pole, over time: https://en.wikipedia.org/wiki/Pole_star#cite_ref-Meeus_6-2
How sure of this are we? Feels like we've can only confirm that's true for a small selection of the vast total.
