The Asteroid Bennu Keeps Spinning Faster and Scientists Aren't Sure Why

[Judi Lynn]

By Meghan Bartels 4 hours ago



The OSIRIS-REx spacecraft's views over asteroid Bennu's north pole, during the probe's early reconnaissance on Dec. 4, 2018.(Image: © NASA/Goddard/University of Arizona)


On a distant space rock being explored by a NASA probe, days are slowly shortening — and scientists are still trying to figure out why.

Right now, the asteroid known as Bennu is spinning once every 4.3 hours. But scientists working on NASA's OSIRIS-REx mission to the space rock have used data gathered before the probe's arrival to calculate that Bennu's rotation rate is speeding up over time — by about 1 second each century.

"As it speeds up, things ought to change, and so we're going to be looking for those things and detecting this speed up gives us some clues as to the kinds of things we should be looking for," Mike Nolan, lead author on the new research and a geophysicist at the Lunar and Planetary Laboratory at the University of Arizona, who is also head of the OSIRIS-REx mission's science team, said in a statement released by the American Geophysical Union, which published the new research. "We should be looking for evidence that something was different in the fairly recent past and it's conceivable things may be changing as we go."

The new research, despite the ties to the OSIRIS-REx mission, isn't based on measurements from that probe; instead, it looks at data collected by two ground-based telescopes between 1999 and 2005 and by the Hubble Space Telescope in 2012. That last data caught scientists' eyes because it didn't line up with predictions astronomers had calculated with the ground-based data.

More:
https://www.space.com/asteroid-bennu-spin-mysteriously-speeding-up.html?utm_source=notification