I’m pretty sure it’s because it’s harder to detect individual stars the farther away from us they are. So you’d expect the stars they found to be clustered around us. We are in the center of that group. The simulation goes back in time to imagine how the stars got to be where they are today.

If the earth was on the other side of the galaxy the group would appear there because the stars we would find would be there. I think the article writer misunderstood the astronomer about this and mismatched responses.

Thanks. I was suspecting that, because seeing stuff through the galactic core is so iffy. But TFA was so damn coy about why they're all on our side. As if it was some deep puzzle.

I'm not an astronomer. But I think that stars in galaxies are supposed to orbit with approximately the same period, independent of distance from the center, due to dark matter distributions.

Almost - stars orbit with approximately the same velocity, not period.

You beat me to it while I was looking for references. =)

"The stars and gas in the Milky Way rotate about its center differentially, meaning that the rotation period varies with location. As is typical for spiral galaxies, the orbital speed of most stars in the Milky Way does not depend strongly on their distance from the center. Away from the central bulge or outer rim, the typical stellar orbital speed is between 210 ± 10 km/s (470,000 ± 22,000 mph). Hence the orbital period of the typical star is directly proportional only to the length of the path traveled."

https://en.m.wikipedia.org/wiki/Milky_Way#Galactic_rotation

So then that's maybe another thing unclear about the video. I'm certainly no reliable source.