Astronomers have transformed star data from the Gaia and Hipparcos missions into a video that predicts stellar motions millions of years from now.
It’s tempting to think of stars as our still companions in the night. But they’re not still at all — stars are moving all the time. It’s just that most of them zoom about the galaxy on timescales too long for humans to appreciate. (Barnard’s Star and Cygnus 61 make for two notable exceptions.)
This video from the European Space Agency takes that appreciation down to our scale, predicting stellar motions 5 million years into the future based on data from the Gaia and Hipparcos spacecraft.
Since July 2014 Gaia has repeatedly photographed the entire sky with the aim of eventually determining precise distances to more than 1 billion stars across the galaxy. Gaia does this by looking for parallax, the slight apparent motion of stars that’s actually due to the spacecraft’s motion in its orbit. (Hold a finger in front of your eyes, then view it with one eye at a time — your finger will appear to move due to the same perspective effect.)
By measuring precise positions, Gaia also sees stars’ proper motions, their movement across the sky. Doppler shifts in spectra measured by other surveys provide the stars’ movement toward and away from Earth, so ultimately we’ll have not just the distances but also the full 3D motion of each of these stars.
That said, Gaia’s still very much in the middle of its mission: The full dataset isn’t expected until 2022. So astronomers don’t have distances and proper motions from Gaia alone just yet. Instead, they’re calculating this information based on early Gaia images, along with previous data from the Hipparcos mission.
The video above shows this selection of 2,057,050 stars seen by both spacecraft and predicts their future motion based on their current positions and velocities. The video is plotted in galactic coordinates, so the plane of the Milky Way spans the center of the image. Orient yourself by Orion (to the right) and the Pleiades (to the left) of the frame.