A Tiny Galaxy Almost Collided With the Milky Way and Astronomers Can See the Effects
A galactic near-miss.
By Charles Q. Choi
Our galaxy’s history was a lot more turbulent than previously thought. In a new paper published in Nature this week, astronomers found that hundreds of millions of years ago, the Milky Way experienced a near collision that churned the motions of millions of stars within its disk.
From our perspective here on Earth, the Milky Way looks like a bright streak of stars against the night sky. But its actual shape is a more complicated spiral, with curving arms reaching out in a disk around a bulging center. The majority of the Milky Way’s stars are located in this disk and not its central bulge. Astronomers generally assumed the disk’s stars moved in a relatively boring, symmetrical manner around the galactic core, having long-since settled into a composed equilibrium in the more than 13 billion years since the galaxy was born.
To learn more about the origin, evolution and structure of the Milky Way, the European Space Agency’s Gaia space observatory is creating a 3-D map of more than a billion stars across the galaxy with unprecedented precision. In the new study, scientists focused on the positions and velocities of six million stars.
