A new observational constraint on the Yarkovsky-driven mobility of main belt asteroids. (arXiv:2006.15170v1 [astro-ph.EP])

A new observational constraint on the Yarkovsky-driven mobility of main belt asteroids. (arXiv:2006.15170v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Dermott_S/0/1/0/all/0/1">Stanley F. Dermott</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Li_D/0/1/0/all/0/1">Dan Li</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Christou_A/0/1/0/all/0/1">Apostolos A. Christou</a> (3) ((1) Department of Astronomy, University of Florida, USA (2) NOIRLab, USA (3) Armagh Observatory and Planetarium, UK)

Small asteroids are lost from the main belt by rotational disruption,
catastrophic collisions, chaotic orbital evolution and evolution driven by
Yarkovsky radiation forces. However, the timescales of these loss mechanisms
are not known. In the inner main belt, the mean sizes of the high-inclination,
non-family asteroids increase with increasing orbital inclination. Here, we
show that this observation is accounted for by the unique resonant structure of
the inner main belt that results in the loss of asteroids through the escape
hatches at the $nu_{6}$ secular resonance and the 3:1 Jovian mean motion
resonance. From the observed asteroid size and orbital inclination
distributions, we show that orbital evolution due to Yarkovsky radiation forces
is the dominant loss mechanism for asteroids with diameters $2 lesssim D
lesssim 7$ $km$. We also show that Yarkovsky-driven orbital evolution accounts
for the observed non-linear size-frequency distributions of the major asteroid
families. From the observed asteroid size and orbital inclination correlation,
we calculate that, on average, over the age of the solar system, the semimajor
axes of the asteroids change on a timescale $lesssim 13.4^{+1.4}_{-1.2}
(D/1,km)$ $Gyr$. This timescale is an upper limit because (a) asteroids
experience collisional evolution and thus their current sizes are mostly less
than their formation sizes and (b) it is possible that the spin directions of
the asteroids have experienced reversals with the result that the sense of
orbital evolution, either towards or away from the Sun, has not been constant.

Small asteroids are lost from the main belt by rotational disruption,
catastrophic collisions, chaotic orbital evolution and evolution driven by
Yarkovsky radiation forces. However, the timescales of these loss mechanisms
are not known. In the inner main belt, the mean sizes of the high-inclination,
non-family asteroids increase with increasing orbital inclination. Here, we
show that this observation is accounted for by the unique resonant structure of
the inner main belt that results in the loss of asteroids through the escape
hatches at the $nu_{6}$ secular resonance and the 3:1 Jovian mean motion
resonance. From the observed asteroid size and orbital inclination
distributions, we show that orbital evolution due to Yarkovsky radiation forces
is the dominant loss mechanism for asteroids with diameters $2 lesssim D
lesssim 7$ $km$. We also show that Yarkovsky-driven orbital evolution accounts
for the observed non-linear size-frequency distributions of the major asteroid
families. From the observed asteroid size and orbital inclination correlation,
we calculate that, on average, over the age of the solar system, the semimajor
axes of the asteroids change on a timescale $lesssim 13.4^{+1.4}_{-1.2}
(D/1,km)$ $Gyr$. This timescale is an upper limit because (a) asteroids
experience collisional evolution and thus their current sizes are mostly less
than their formation sizes and (b) it is possible that the spin directions of
the asteroids have experienced reversals with the result that the sense of
orbital evolution, either towards or away from the Sun, has not been constant.

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