のを知った

learned that; found out that

→ の

phrase Uncommon #8,262

learned that; found out that の turns the preceding clause into a fact or event that someone learns about.

JA: 新聞で彼が南極から帰って来たのを知った。

EN: I learned from the newspaper that he had returned from Antarctica.

I learned from the newspaper that he had returned from Antarctica.

I found out there was a cute girl nearby.

I found the book boring.

However, I now know that it still exists.

— 帰ってきたヒトラー (2015)