A NASA spacecraft reached a space rock and found it orbited by tiny moons—a phenomenon “never been seen before in any solar-system object.”
Billions of years ago, something—perhaps the vibrations of an exploding star—jostled a cloud of cosmic gas and dust suspended in space. The cloud collapsed on itself and flattened into a spinning disk. The center grew heavy and ignited, forming our sun. The stuff that remained ricocheted, collided, and congealed. The biggest clumps of space stuff smoothed into spheres—the planets and moons. The smallest, the asteroids and comets, stayed as they were, like crumbs left over from an elaborate feast.
And right now, one of those crumbs is exploding.
An asteroid named Bennu has been caught spewing particles into space—hundreds of gravel-sized bits, hurtling from the surface at high speed.
The tiny explosions were spotted by a NASA spacecraft named OSIRIS-REx. The probe settled into an orbit around the asteroid in late December and noticed the first ejection within days. Over the next two months, OSIRIS-REx observed nearly a dozen of these events. And more are still being detected.