Dinkinesh is a small asteroid orbiting the Sun near the inner edge of the main asteroid belt. NASA’s Lucy spacecraft recently revealed the asteroid, which has an effective diameter of only 720 m, to be unexpectedly complex: it has a prominent trough overlain by a equatorial ridge and is orbited by a contact binary satellite, now named Selam. This satellite consists of two near-equal-sized lobes with diameters of 210 m and 230 m. It orbits Dinkinesh at a distance of 3.1 km with an orbital period of about 52.7 hours and is tidally locked.
“We want to understand the strengths of small bodies in our Solar System because that’s critical for understanding how planets like Earth got here,” said Lucy principal investigator Dr. Hal Levison, a researcher at the Southwest Research Institute.
“Basically, the planets formed when zillions of smaller objects orbiting the Sun, like asteroids, ran into each other.”
“How objects behave when they hit each other, whether they break apart or stick together, has a lot to do with their strength and internal structure.”
The researchers think that Dinkinesh is revealing its internal structure by how it has responded to stress.
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.
This event likely caused debris to enter into a close orbit, which became the raw material that produced the ridge and satellite.
If Dinkinesh were much weaker, more like a fluid pile of sand, its particles would have gradually moved toward the equator and flown off into orbit as it spun faster.
However, the images suggest that it was able to hold together longer, more like a rock, with more strength than a fluid, eventually giving way under stress and fragmenting into large…
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