Homing in for New Year: impact parameters and pre-impact orbital evolution of meteoroid 2014 AA

Abstract

On 2008 October 7, small asteroid $2008~\mbox{TC}_{3}$ turned itself into the parent body of the first meteor ever to be predicted before entering the Earth’s atmosphere. Over five years later, the 2014 AA event became the second instance of such an occurrence. The uncertainties associated with the pre-impact orbit of $2008~\mbox{TC}_{3}$ are relatively small because thousands of observations were made during the hours preceding the actual meteor airburst. In sharp contrast, 2014 AA was only observed seven times before impact and consequently its trajectory is somewhat uncertain. Here, we present a recalculation of the impact parameters—location and timing—of this meteor based on infrasound recordings. The new values—$(\lambda_{\mathrm{impact}}, \phi_{\mathrm{impact}}, t_{\mathrm{impact}}) = (-44^{\circ }, +11^{\circ }, 2456659.618~\mbox{JD UTC})$—and their uncertainties together with Monte Carlo and $N$-body techniques, are applied to obtain an independent determination of the pre-impact orbit of 2014 AA: $a=1.1623~\mbox{AU}$, $e=0.2116$, $i=1.\hspace {-0.3em}^{\circ}4156$, $\varOmega =101 .\hspace {-0.3em}^{\circ}6086$, and $\omega=52.\hspace {-0.3em}^{\circ}3393$. Our orbital solution is used to investigate the possible presence of known near-Earth objects (NEOs) moving in similar orbits. Among the objects singled out by this search, the largest is $2013~\mbox{HO}_{11}$ with an absolute magnitude of 23.0 (diameter 75–169 m) and a MOID of 0.006 AU. Prior to impact, 2014 AA was subjected to a web of overlapping secular resonances and it followed a path similar to those of $2011~\mbox{GJ}_{3}$, $2011~\mbox{JV}_{10}$, $2012~\mbox{DJ}_{54}$, and $2013~\mbox{NJ}_{4}$. NEOs in this transient group have their orbits controlled by close encounters with the Earth–Moon system at perihelion and Mars at aphelion, perhaps constituting a dynamical family. Extensive comparison with other studies is also presented.

Appendices

Appendix A: Orbital elements of the Earth around the time of impact

Chesley et al. (2015) have released the impact time and the hypocentre location for the 2014 AA impact (see their Table 1) as included in the REB of the IDC of the CTBTO for 2014 January 2. The impact time was 2014 January 2 at 3:05:25 UTC with an uncertainty of 632 s. The impact location coordinates were latitude (${^{\circ }}\mbox{N}$) equal to $+14.\hspace {-0.3em}^{\circ}6326$ and longitude (${^{\circ }}\mbox{E}$) of $-43.\hspace {-0.3em}^{\circ}4194$. Therefore, the actual impact with the atmosphere took place at epoch 2456659.629537 Julian Date, Barycentric Dynamical Time. The uncertainty is about 10 minutes. The osculating orbital elements of the Earth within $\pm150~\mbox{s}$ of the detection are given in Table 10. These values have been computed by the SSDG, Horizons On-Line Ephemeris System.

Table 10 Orbital elements of the Earth around JD 2456659.629537 = A.D. 2014-Jan-02 03:06:32.00 TDB (Source: JPL Horizons system). Data as of 2016 April 12

Appendix B: Cartesian state vectors at epoch JD TDB 2456658.628472222 = A.D. 2014-Jan-1 03:05:00.0000 TDB

In order to facilitate verification of our results by other astrodynamicists, we show in Table 11 the Cartesian state vectors of the physical model used in all the calculations presented here. These values have been computed by the SSDG, Horizons On-Line Ephemeris System at epoch JD TDB 2456658.628472222 = A.D. 2014-Jan-01 03:05:00.0000 TDB, this instant is considered as $t = 0$ across this work unless explicitly stated. Positions and velocities are referred to the barycentre of the Solar System.

Table 11 Cartesian state vectors at epoch JD TDB 2456658.628472222 that corresponds to 03:05:00.0000 TDB on 2014 January 1 (Source: JPL Horizons system, data as of 2016 April 12). The sample Cartesian vector for 2014 AA corresponds to the nominal orbit in Table 5