Constraining Yarkovsky Acceleration With Thermophysical Modeling
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2023
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The Yarkovsky effect is a phenomenon that arises from an anisotropy in an asteroid's surface temperature distribution and resulting thermal emission that induces a secular change on the asteroid's semimajor axis, causing the asteroid to drift outwards or inwards in its orbit. It is the main mechanism by which the near-Earth asteroid population is maintained, where main belt asteroids (MBAs) are continuously moved into powerful resonances that eject them into near-Earth orbits. Despite hundreds of successful detection among near-Earth asteroids (NEAs), the Yarkovsky effect has never been detected in MBAs before.
The Yarkovsky effect is difficult to predict as it relies on several physical parameters that are often completely unconstrained, but these parameters can be derived by way of thermophysical modeling. Using thermal flux measurements obtained by the Wide-field Infrared Survey Explorer (WISE) combined with shape models and spin information from the Database of Asteroid Models from Inversion Techniques (DAMIT), we obtained newly derived diameters, albedos, and thermal inertia for nearly 2000, primarily main belt, asteroids. With the parameters in hand, we were able to use a rudimentary Yarkovsky model to estimate the acceleration imparted to each of our asteroids. We attempted to confirm our predictions with the University of Hawai'i 88-inch telescope, where we observed a total of 135 MBAs and two NEAs in order to supplement the astrometric data drawn from the Minor Planet Center.
Using the OrbFit software package to compute our asteroids' orbits, we found Yarkovsky signal strengths consistent with previous studies for our two NEAs. However, we were unable to find any reliable detections of Yarkovsky in our sample of MBAs due to the limitations of the historical astrometric data. Through tests with synthetic observations, we were able to identify the minimum observational arc length with modern astrometric accuracy needed to detect Yarkovsky for not only all of our sample MBAs, but also any theoretical MBA of a given size and semimajor axis, estimating that Yarkovsky should be detectable within a couple of decades for a 100-m MBA, a size range which should be detectable by the near-future Vera Rubin Observatory Legacy Survey of Space and Time. While current technology is not yet at a sufficient level to detect Yarkovsky in the main belt, the future is promising, especially with the gamut of upcoming infrared and wide-field surveys that will enable even more thermophysical modeling of higher precision in the future.
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Astronomy, asteroids, orbits
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