New NASA image of unusual asteroid reveals it has its own moon

NASA's Lucy is a space probe sent to explore an array of small asteroids trapped in Jupiter's orbit. As the space agency explains, the two "swarms" of asteroids "may be 'fossils' from the era of planet formation." Now, images from a fly-by of one of the small asteroids, named Dinkinesh, reveals that it has its own small moon. They've dubbed that satellite Selam, an Amharic greeting meaning "peace." Interestingly, the moon is actually two hunks of rock touching each other, known as a "contact binary." How it formed into this configuration a mystery.

Along with Selam, the images show a ridge and the spot where a huge chunk Dinkinesh—around a quarter of it—moved to give the asteroid its unusual shape.

"Over millions of years rotating in the sunlight, the tiny forces coming from the thermal radiation emitted from the asteroid's warm surface generated a small torque that caused Dinkinesh to gradually rotate faster, building up centrifugal stresses until part of the asteroid shifted into a more elongated shape," NASA states. "This event likely caused debris to enter into a close orbit, which became the raw material that produced the ridge and satellite."

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