Asteroid Bennu, OSIRIS-REx mission

Asteroids are rocky, airless worlds that orbit our Sun but are too small to be called planets. Tens of thousands of these minor planets are gathered in the main asteroid belt, a vast doughnut-shaped ring between the orbits of Mars and Jupiter. Asteroids that pass close to Earth—and merit close watch—are called Near-Earth Objects, or NEOs.

The currently known asteroid count is 781,692.