Because what makes it glow is actually solar wind from our sun as it passes through the solar system.

For possibly billions of years, it has simply been an inert lump of ice passing through the universe.

It could be extra-galactic. It's going at a fair clip, and (if I haven't dropped a zero or ten) it would only take around 800 million years to get here from one of the Magellanic Clouds.

Just as an indicator of the speed and possible distances.

> “But based on the researchers’ analyses of the interstellar object’s vertical motion in the galaxy (its path is known to weave up and down in the galactic disk), they concluded that it likely originated from the Milky Way’s thin disk, not its thick disk as was mentioned some months ago. The thin disk contains somewhat younger objects than the thick disk.”