The acceleration of the solar system: This one is incredibly cool, and is lead by Sergei Klioner (Dresden). The acceleration of the solar system due to everything outside it has been directly measured for the first time! #GaiaEDR3 ( https://www.cosmos.esa.int/documents/29201/5015079/AccelerationSolarSystem_Accepted.pdf/74dc1784-bc83-42b2-e6cb-5004ad07305e?t=1606986122895)

We can do this because it produces a predictable signature in the proper motions of quasars across the sky, purely because of relativity. It points in the direction we're accelerating (image credit: Klioner)

But the expected acceleration is tiny. 0.2 nm/s^2, or 7 km/s/Myr, which is an maximum astrometric effect of 5 microarcseconds/year!

My job on the paper was to put together estimates of what we expect given what we know about the Galaxy. We expect it to be directed towards the Galactic centre, with the biggest pull away from that being from the LMC.

We’ve measured it! It fits our expectations very well. No chance to measure the effect of the LMC (or other disturbances) this time, but it should be possible with future Gaia data releases.

7.32±0.51 km/s/Myr towards the Galactic centre, with the other components consistent with zero (with similar error bars).