Rotational changes of the asteroid 99942 Apophis during the 2029 close encounter with Earth
J. Souchay et al. (2014)
- Published
- Mar 1, 2014
- Journal
- Astronomy & Astrophysics · Vol. 563
- DOI
- 10.1051/0004-6361/201322364
At a GlanceAI
Estimates Earth’s 2029 tidal torques could shift Apophis’ spin pole by degrees, potentially triggering detectable tumbling.
SummaryAI
The paper quantifies how Earth’s 2029 flyby can reorient Apophis’ spin axis—an effect less studied than the encounter’s orbital deflection but crucial for interpreting post-flyby lightcurves and radar shape modeling. Using a rigid-body torque model, it predicts degree-scale changes in precession and obliquity over only a few hours, with outcomes strongly controlled by Apophis’ (unknown) polyhedral shape via its dynamical ellipticity and by the encounter geometry. These rapid pole shifts imply a real possibility of entering or enhancing a non-principal-axis (tumbling) state, and they set concrete, observation-facing targets for detecting rotational excitation during the flyby. The results also matter because any post-encounter spin-state change feeds back into thermal forces (Yarkovsky) used to assess long-term impact risk.
Method SnapshotAI
Numerically integrates a Kinoshita-style rigid-body gravitational-torque model over the close-approach ephemeris to compute changes in precession and obliquity.
BackgroundAI
Background in rigid-body rotation (precession/nutation), tidal torques, and basic asteroid physical modeling (moments of inertia/shape).
Apophis physical model
— SA