Amor 2002 RN38

This NEO is listed in the page of Asteroids with Comet-Like Orbits maintained by Y. Fernandez.

It was also discussed as an object with a likely cometary origin in some papers, among which I found:

• "On Near-Earth Asteroid Study at Department of  Astronomy, Bandung Institute of Technology" by S. Siregar.
• "Assessing the physical nature of near-Earth asteroids through their dynamical histories" by Julio A. Fernández, Andrea Sosa, Tabaré Gallardo, Jorge N. Gutiérrez.

At the time I made this analysis, this Amor was last observed on November 11th, 2017 and the orbit uncertainty is 0 being based on 119 observations acquired in the last 15 years.

JPL Small-Body Database Browser:

Orbital Elements at Epoch 2458000.5 (2017-Sep-04.0) TDB
Reference: JPL 31 (heliocentric ecliptic J2000)

Element Value Uncertainty (1-sigma)   Units  e .6730769823381273 2.1793e-07 a 3.820825408551513 1.2346e-07 au q 1.249115772522818 7.9678e-07 au i 4.160437503290696 1.756e-05 deg node 296.1904517164833 0.00024613 deg peri 118.6156866423836 0.00026072 deg M 357.1006606538095 3.1062e-05 deg tp 2458022.470035828635 (2017-Sep-25.97003583) 0.00023642 JED period 2727.936248200967 7.47 0.00013222 3.62e-07 d yr n .1319678933983206 6.3964e-09 deg/d Q 6.392535044580208 2.0656e-07 au

Orbit Determination Parameters    # obs. used (total)      119      data-arc span      5568 days (15.24 yr)      first obs. used      2002-08-18      last obs. used      2017-11-15      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      0      fit RMS      .55328      data source      ORB      producer      Otto Matic      solution date      2017-Nov-16 07:18:58   Additional Information  Earth MOID = .270556 au   Jupiter MOID = .260678 au   T_jup = 2.626

I simulated 100 clones of this asteroid in the past 10^8 days trying to confirm its possible cometary origin: the goal is to determine whether some clones might have arrived from the outskirt of the solar system - arbitrary threshold: 100 AU.

Simulation approach

Mercury6 Integrator

reference:

J.E.Chambers (1999) 

A Hybrid Symplectic Integrator that Permits Close Encounters between Massive Bodies''. Monthly Notices of the Royal Astronomical Society, vol 304, pp793-799.

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

   Algorithm: Bulirsch-Stoer (conservative systems)

   Integration start epoch:         2458000.5000000 days
   Integration stop  epoch:      -100000000.0000000
   Output interval:                     100.000
   Output precision:                 medium

   Initial timestep:                0.050 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

• 79 out of 100 clones have a cometary like orbit.
• of which: 13 came on a hyperbolic orbit (Vinfinity = 42.1219*sqrt(-0.5/a) --> the minimum absolute value for semi-major axis a was -17.46 AU -->the maximum value for Vinfinity was 7.14 km/s 
• 1 out of 100 was discarded because "hit" the sun (due to extremely high eccentricity).

The time when they entered the solar system was distributed as follows:

   Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
-272319 -151956  -85380 -100222  -38660    -370

In a graphical form:

The most recent arrival in the solar system could have happened a relatively short time ago compared to other asteroids with a cometary like orbit: year 370 B.C.

A look at the nominal asteroid

The nominal asteroid is one of the 79 clones with a cometary like orbit. It apparently arrived in the solar system about in year 87000 B.C 

In the following plots (made with R package ggplot2), the vertical dashed lines show a close encounter with Jupiter.

Close Approaches analysis
For every given planet, every clone had a certain number of close approaches so we can calculate the mean number of close approaches and the mean number of Dmin (distance of the close approach). Even better, we can print a boxplot showing the distribution of the number of close approaches and their distances.

Kind Regards,
Alessandro Odasso

Asteroid 2017 DQ15

Asteroid 2017 DQ15 is a NEO (Apollo) displayed in the list of objects with a comet-like orbit maintained by Y. Fernandez.

Orbital Elements at Epoch 2458000.5 (2017-Sep-04.0) TDB
Reference: JPL 7 (heliocentric ecliptic J2000)

Element Value Uncertainty (1-sigma)   Units  e .7272164269790051 1.279e-05 a 2.823784780342436 0.00011852 au q .7702821018241148 3.8782e-06 au i 20.18557131636563 0.00017551 deg node 272.8777420846461 0.00046785 deg peri 350.4179039106148 0.00040687 deg M 22.44168793940112 0.0013623 deg tp 2457892.456452631231 (2017-May-18.95645263) 0.00026204 JED period 1733.18857109974 4.75 0.10912 0.0002988 d yr n .207709654911683 1.3077e-05 deg/d Q 4.877287458860757 0.00020471 au

Orbit Determination Parameters    # obs. used (total)      43      data-arc span      187 days      first obs. used      2017-02-10      last obs. used      2017-08-16      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      5      fit RMS      .50315      data source      ORB      producer      Otto Matic      solution date      2017-Aug-17 06:19:02   Additional Information  Earth MOID = .22774 au   Jupiter MOID = .339108 au   T_jup = 2.792

Based on the nominal orbital parameters and uncertainty, I generated 100 clones with an R script and then I used the Mercury6 simulator by J.E. Chambers to investigate what happened in the last 10^8 days.

Mercury6 simulator: configuration

More about the program "A Hybrid Symplectic Integrator that Permits Close Encounters between Massive Bodies'' can be found here.

Main integration parameters:

   Algorithm: Bulirsch-Stoer (conservative systems)

   Integration start epoch:         2458000.5000000 days
   Integration stop  epoch:        -10^8 days
   Output interval:                     100.000 days
   Output precision:                   medium
   Initial timestep:                      0.100 days
   Accuracy parameter:             1.0000E-12
   Ejection distance:                  1.0000E+02 AU

Simulation results

As seen above, the "ejection distance" used to claim that an asteroid has arrived from the outskirts of the solar system is 100 AU.

The simulation shows that there is a good likelyhood that the asteroid has a cometary origin:

• 47 out of 100 clones arrived from a distance greater than 100 AU in the last 10^8 days
• 4 out of 100 clones would have "collided" with the sun 

The most recent arrival time was about 7906 B.C.

The mean arrival time was about 139274 B.C.

The less recent arrival time was about 268318 B.C.

The arrival time distribution of the 47 clones that were likely to be comets is shown below:

Kind Regards,

Alessandro Odasso