astro: Asteroid 2018 LF5

Asteroids 2018 LF5 is an Amor (PHA) that had a relative close approach with earth yesterday July 7th, 2018.

Its orbit is still uncertain (condition code 6).

At the time of writing, it seems that this Amor has some potential to have a cometary origin. More details below.

Clones Generation

I generated 100 clones trying to achieve an orbital parameter distribution (mean and 1-sigma) that matches as far as possible the target nominal data read from Horizons Web a few hours ago on July 6th.

This is a comparison table that shows the clones distribution versus the target one:

	clones_mean	clones_sd	target_mean	target_sd
q	1.06373506	3.2E-06	1.06373514	3.21E-06
e	0.61855794	7.847E-05	0.61856034	7.85E-05
i	41.04180418	0.001757	41.04185685	0.0017567
peri	181.03405996	0.00019308	181.03405317	0.00019281
node	100.75809149	0.00030458	100.75808179	0.00030512
tp	2458309.05107042	0.00017576	2458309.05106226	0.0001761

Backward simulation
I used the Mercury Integrator by John E. Chambers (with some subroutines supplied by Hal Levison and Martin Duncan).

           Integration parameters
           ----------------------

   Algorithm: Bulirsch-Stoer (general)

   Integration start epoch:         2458200.5000000 days
   Integration stop epoch:      -100000000.0000000
   Output interval:                     100.000
   Output precision:                 medium

   Initial timestep:                 .050 days
   Accuracy parameter:              1.0000E-12
   Central mass:                    1.0000E+00 solar masses
   J_2:                              0.0000E+00
   J_4:                              0.0000E+00
   J_6:                              0.0000E+00
   Ejection distance:               1.0000E+02 AU
   Radius of central body:          5.0000E-03 AU

Simulation results
LF_91    ejected at     -60075 9 16.03454
sun was hit by LF_54    at    -112260 1 30.7
sun was hit by LF_38    at    -115727 5 28.2
sun was hit by LF_72    at    -117581 3 8.3
sun was hit by LF_17    at    -133748 2 27.5
sun was hit by LF_46    at    -136245 9 8.1
LF_63    ejected at    -144164 7 8.61087
sun was hit by LF_61    at    -149555 10 11.3
sun was hit by LF_69    at    -174783 1 21.9
LF_48    ejected at    -193993 10 9.15850
sun was hit by LF_71    at    -194558 6 14.5
LF_84    ejected at    -218748 7 12.96343
sun was hit by LF_81    at    -222146 6 1.6
sun was hit by LF_43    at    -225535 3 27.2
LF_39    ejected at    -235862 11 1.20080
sun was hit by LF_28    at    -240288 5 16.1
LF_20    ejected at    -244214 1 9.02367
LF_95    ejected at    -245994 9 18.71844
LF_100   ejected at    -262161 2 11.44480
sun was hit by LF_65    at    -265855 6 9.3
LF_77    ejected at    -269187 3 12.79012
LF_11    ejected at    -277829 10 18.10824

The same information can be displayed in a graphical form, where we can see that the number of clones (initial number 100) is decreasing as you go in the past:

Simulation Graphs

In the following graphs, the simulation period was divided into 10 intervals.

In every interval, the maximum value of the relevant orbital parameter was found for every clone and all clones values are finally displayed in a boxplot.

Orbit Specific energy

In the picture below:
energy = 0 parabolic orbit
energy > 0 hyperbolic orbit
energy <0 elliptical orbit