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Asteroid Bennu: Changes in Rotation Rate

14 Mar 2019, 17:29 UTC
Asteroid Bennu: Changes in Rotation Rate
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Tuesday’s post on asteroids and what it would take to deflect or destroy one has been usefully reinforced by a new paper from Mike Nolan (Lunar and Planetary Laboratory, University of Arizona) and colleagues, who discuss their findings in Geophysical Research Letters. Here we’re looking at observations of the near-Earth asteroid (101955) Bennu, both archival (extending back to 1999) and current, drawing on the OSIRIS-REx mission.
You’ll recall that OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) is in operation around the asteroid, its observations helping us understand the object’s rotation, structure and composition, with a sample return planned for 2023. The Nolan paper fills us in on observed changes in rotation, which are apparent on the order of about 1 second per century. The asteroid’s rotation is speeding up.
Exactly what’s going on here is something we can hope OSIRIS-REx can help nail down. One possibility is a process like the Yarkovsky‐O’Keefe‐Radzievskii‐Paddack effect (YORP), by which asteroids are known to be affected because of the uneven distribution of solar heating across their surfaces. The effects of YORP depend on the shape and orientation of the individual asteroid and can cause either a slowdown or uptick in the ...

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