What primary observational challenge causes uncertainty in precisely counting stars within the Milky Way?

Answer

Obscuring dust and gas absorbing visible light

Looking through the galaxy means that immense clouds of obscuring dust and gas absorb and scatter visible light, which makes distant stars appear fainter or completely invisible, biasing counts toward closer, brighter stars.

What primary observational challenge causes uncertainty in precisely counting stars within the Milky Way?

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How Many Planetary Systems Are In The Milky Way? - Physics Frontier

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