If you've noticed tweets from people you don’t follow popping up on your Twitter timeline, you’re not going crazy.
Twitter has updated its help document with information explaining why new tweets, in addition to sponsored tweets and ads, now show up in your timeline, in addition to the regular digest of tweets from Twitter accounts that you follow.
“When we identify a Tweet, an account to follow, or other content that's popular or relevant, we may add it to your timeline. This means you will sometimes see tweets from accounts you don't follow. We select each Tweet using a variety of signals, including how popular it is and how people in your network are interacting with it. Our goal is to make your home timeline even more relevant and interesting,” says the updated document.
Importantly, favoriting something is not the sole decider in whether the new tweet shows up on your timeline.
TIME could not immediately confirm with Twitter what, exactly, qualifies a tweet as "popular or relevant," but it seems to involve how many retweets and favorites something gets--meaning that the once relatively impotent little star next to a tweet has just been given new--if rather ambiguous--life.