The European Space Agency’s Gaia mission is revolutionizing our picture of our home Galaxy, the Milky Way. Astronomers exploring measurements of the positions of over 2 billion stars which ESA gave to the world in Gaia’s Data Release 2 (DR2) have confirmed how the vast disk of our Galaxy is not only rotating, but also bending up and down as ripple-like features spread outwards.
On June 13th 2022, ESA announced its latest data released (DR3). This included a subset of 35 million close to our own Sun, with precise measurements of their 3-D positions and 3-D motions. A team of local Milky Way experts, including Prof. Kathryn Johnston in the Columbia Astronomy Department, were able to use this data set to uncover exquisite evidence of expansion and contraction perpendicular to the inner disk - a breathing motion.
The image shows the pattern of density of stars in position (x-axis) and motion (y-axis) perpendicular to the disk which support this discovery. The clear, 2-armed spiral is evidence of stars near the disk collectively moving away and towards the plane with shorter periods than those further away. For more details see: https://arxiv.org/abs/2206.06125
The emerging picture of the Milky Way is that our Galaxy is not sitting idly in space, but rather is gently exercising.