Eli5: is it possible to know if there are galaxies hidden behind galaxies closer to us? And if yes, can we look at them with current technologies?
In: Planetary Science
The Simplest answer is: Sometimes.
The scale of the universe means it’s all but certain that (for example) there are galaxies on the other side of Andromeda that we can’t see.
However galaxies are heavy things, heavy enough to bend space around them, so that sometimes the light from a galaxy on the far side get’s bent around the foreground galaxy and we can still see it. It’s called gravitational lensing, and this sometimes let’s us see things we ordinarily wouldn’t be able to.
Usually. Stars are incredibly small compared to the distances between them. Entire galaxies and pass through others without a single star colliding. Our own will be doing this with Andromeda in about 4.5B years but they’ll likely merge.
So when we look at distant galaxies, the stars we’re looking at can easily be ones that are closer or further away than the galaxy we see. We can calculate a star’s distance using parallax, red shift etc to work out which “dots” are part of the galactic cluster we’re examining.
But as for looking at an entire galaxy that might be behind another, we run into resolution and other limits in discerning that level of detail. So the practical answer is “usually not”.
We actually cannot even see the other side of the Milky Way very well. We somewhat extrapolate there to get the shape as the many stars and clouds near the center blocks the view in a huge part of the spectrum.
In particular: yes. With the galaxy close to us being the Milky Way itself even.
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