The Galaxy's Spin Is Hiding in the Hum of Gravitational Waves

We are used to thinking of gravitational waves as messengers from catastrophes in space, the ringing of spacetime after black holes collide for example. But our own Galaxy hums with a fainter, steadier signal, a chorus of millions of unseen binary stars. A new study has found that this hum carries a hidden fingerprint of the Milky Way's spin, and that if a future space mission ignores it, our picture of the Galaxy itself could come out subtly wrong.