I’ve read that the Pisces constellation lies outside the Milky Way Galaxy (I think what I read is that it’s separated from the Milky Way by the Square of Pegasus), but I’ve also read that all of the constellations of the Zodiac *are* in our galaxy. So which is true?
Yes all the stars you can see in the sky are within the Milky Way
It’s a safe bet that ANY individual star that can be seen is within the Milky Way Galaxy. Any other galaxy is waaaaaayyyyyy to far away to see any individual star within it. Some of the “stars” in the constellation are actually other galaxies (and maybe that’s what was meant by being “outside the Milky Way Galaxy”) (M74 is the most visible galaxy in Pisces), but all of the actual, individual stars that you see are within the Milky Way Galaxy.
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Yes, all the stars we can see with our naked eyes are within the Milky Way Galaxy. What you read must have been referring to the main body of the Milky Way, which is seen from dark locations as a faint milky band across the sky, as opposed to the nearby Milky Way stars which are all around us.