How GPI Works to See Planets

I sometimes compare the challenge of directly detecting a Jupiter orbiting a nearby star to finding a glowing needle in a haystack.  Oh, and by the way, the haystack is on fire.

It’s about as hard as seeing a candle a foot away from a spotlight (1 million candlepower) at a distance of 100 miles.

Why is doing this so difficult?  There are three primary reasons: