On a distant space rock investigated by NASA's probe, the days are slowing down – and scientists are still trying to figure out why. every 4.3 hours. But scientists working on NASA's OSIRIS-REx mission to space rock used data collected before the probe arrived to calculate that Bennu's rotation speed accelerated over time – by about 1 second of every century. As things accelerate, things need to change, so we'll look for these things, and discovering that speed gives us some insights into what kinds of things we need to look for, "Mike Nolan, lead author of the New Study and Geophysicist in the Moon and Planetary a laboratory at the University of Arizona, who is also the head of the OSIRIS-REx mission team, said in a statement published by the American Geophysical Union, which published the new study. "We have to look for evidence that something is different in the relatively recent past and it is possible to change things when we go." Related: OSIRIS-REx: NASA Mission to Return Asteroids to Photos
The new study, despite mission links OSIRIS-REx is not based on measurements from this probe; Instead, he looks at data collected from two terrestrial telescopes between 1
"You can not make all three of them fit completely," said Nolan. "It was when we came up with this idea that it should speed up."
This is not an unknown phenomenon, but it is rare, and scientists have just confirmed their first example of accelerating the rotation of the asteroid in 2007. Bennou observations leave the secret to what causes it.
One possible explanation is that the material that moves on the surface of Bennu or emerges from the asteroid can allow the speed of rotation to accelerate. The other explanation is more complex, the effect Yarkovski-O'Keefe-Radzievski-Paddak (YORP) . This effect is caused by the sunlight rebounding from the asteroid and slightly changing the spin speed faster or slower depending on the shape of the object. For particularly weak asteroids, the effect of YORP can actually break into a rock space .
Scientists behind the new study suspect that the effect of YORP Bennu is experiencing. Over the next two years, OSIRIS-REx will provide more data, including detailed boulder analysis and gravity measurements. Scientists can use these observations to confirm what is happening in Bennu and determine the local YORP levels.
These numbers can also help scientists understand the behavior of other asteroids who will never see a special spacecraft.  published January 31 in Geophysical Research Letters.