[larperdoodle]

The star is occulted by a small asteroid in our solar system. For something in the Betelgeuse system to occult the star, it would have to be about the same size as the star.

We detect the presence of planets in other systems when they pass between us and the star, marginally decreasing the brightness.

Not a great way to send messages long distances

[midasuni]

If a star vanishes because you build a Dyson sphere that’s one way of sending a message

[spartanatreyu]

No need to build a whole Dyson Sphere, a simple starshade will do.