More than 35 years after its launch, Voyager 1 is finally leaving the neighbourhood. Now 18 billion kilometres from Earth, the 722 kilogram vessel just left our solar system.
Or did it? Scientists at Nasa and elsewhere are debating that claim. Road signs are scarce out there, but they are seeing some signals, but not others, of changes in the cosmic-ray and magnetic field environment that defines the boundary.
In a sense it doesn't matter. Voyager is still going, and will be beyond our sun's system soon enough.
No human-made object is farther away from home than Voyager, and with its 18bn km head start nothing will catch up, until very different new propulsion methods are discovered.
Next stop: the neighbourhood of Gliese 445, in the constellation Camelopardalis. Some 40,000 years from now, if it survives, Voyager will pass within 1.6 light years of that star. Will anyone be home? If so, the Gliesians may be able to get into Voyager's cache of Earth souvenirs, including a recording of Chuck Berry's song Johnny B Goode.
If they do, we might be glad they're so far away. If by chance they don't like that tune, it will take them a long time to deliver their revenge.