Chemical Cartography Reveals the Milky Way’s Spiral Arms

This is an example: https://youtu.be/TXWuZSWtDPE.

The first part of the video shows the parallax effect, in which stars appear to follow circles on the sky as the Earth orbits the Sun. Stars that are closer to us appear to move more, while stars that are far away hardly appear to move at all. The parallax effect is how Gaia measures distances to stars throughout the Milky Way. Gaia is the first instrument capable of measuring the parallax effect for stars thousands of lightyears away, all the way to the center of the Milky Way. In the video, the parallax effect has been exaggerated by some incredible factor so that you can see it. In reality, Gaia is measuring parallaxes as small as ten billionths of a degree, roughly.

The second part of the video shows the motion of stars in the Galaxy, projected out millions of years into the future. We get so used to the stars in the sky being static that it's easy to forget that they're all hurtling through the Galaxy at speeds of about 200 kilometers per second. The sky only appears to be static because the distances involved are huge compared to the orbital speeds of the stars. Just for context, it takes the Sun about 200 million years to complete one orbit of the Milky Way. In the 80 or so years each of us gets on this planet, the Sun completes less than a millionth of its orbit, so the sky appears almost perfectly static - unless you have an instrument like Gaia, that can measure angles of a few tens of billionths of a degree.

Finally, I'll note that even though the video doesn't show a photo taken by Gaia, it is generated using real data from Gaia. Every star shown in the video is a real star that Gaia has taken measurements of.