Rigel wasn't "discovered" in the sense that a new object was found. It's been visible to the naked eye since ancient times and was likely known to humans long before recorded history.

Here's why:

* Brightness: Rigel is one of the brightest stars in the night sky, making it impossible to miss.

* Ancient Astronomy: Many ancient civilizations (Egyptians, Greeks, Babylonians, etc.) were skilled astronomers and charted the stars. Rigel, as a prominent star in Orion, would have been a part of their celestial maps.

Therefore, while we can't pinpoint an exact date of "discovery," Rigel has been known and observed for millennia.