YORP effect apparently has made this asteroid spin so fast, it's breaking up.
"[S]unlight [i.e., the YORP effect] can spin up an asteroid, making it rotate faster. That's no big deal in the short term, but in the long run it spells disaster: At some point the rock is spinning so rapidly that the centrifugal force outward on its surface balances the gravitational force inward. If you're a rock sitting on the surface, over time as the asteroid spins faster you feel less and less gravity. You weigh less!
Is this what's happening to Gault? Observations from the ground indicate it has a rotation rate of about 2 hours, and it turns out that's almost exactly where you expect the rotational speed to start causing effects like this! Also, the dust is leaving the asteroid relatively slowly, at speeds of under a meter per second (less than walking speed). That's also about what you'd expect from dust launched into space by a landside (and the rotational speed of the asteroid on the surface near the equator is about 2 meters per second, which also gives the dust a kick).
It all adds up: Gault has been getting spun up by the ethereal breeze of light from the Sun, and is now very close to the point where it'll fly itself apart."
#Science #Space #Astronomy #Asteroids #Dynamics #YorpEffect