Harvard Astrophysicist Avi Loeb joins! What exactly is this Space Object '3I/Atlas' that has been identified?

How much time?! Loeb: "It's the size of Manhattan Island." What exactly is this Space Object '3I/Atlas' that has been identified?
"That's not much smaller than the asteroid that killed the dinosaurs"- Harvard Astrophysicist Avi Loeb joins!