Asteroid 2017 RS - an extinct comet?

Asteroid 2017 RS was first observed at Pan-STARRS 1, Haleakala on 2017-09-01. 

It is classified as a Mars-crosser.

Its orbit is still very uncertain (condition code 9).

It would be nice to have more data because this asteroid may be an extinct comet.

Orbital data

From JPL Small-Body Database Browser we can see:

(2017 RS)

Classification: Outer Main-belt Asteroid          SPK-ID: 3781340

[ Ephemeris | Orbit Diagram | Orbital Elements | Physical Parameters ]

[ show orbit diagram ]

Orbital Elements at Epoch 2457998.5 (2017-Sep-02.0) TDB Reference: JPL 1 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .6145637063005263 0.020702 a 4.14837857496493 0.18924 au q 1.598935662796787 0.016606 au i 16.490996995339 0.23653 deg node 221.6460003522266 0.96443 deg peri 165.4311035552846 2.8664 deg M 351.0338219139737 0.34606 deg tp 2458075.363624646766 (2017-Nov-17.86362465) 2.4617 JED period 3086.142680565361 8.45 211.17 0.5782 d yr n .1166504718874665 0.0079819 deg/d Q 6.697821487133073 0.30553 au

Orbit Determination Parameters    # obs. used (total)      18      data-arc span      5 days      first obs. used      2017-09-01      last obs. used      2017-09-06      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      9      fit RMS      .20988      data source      ORB      producer      Otto Matic      solution date      2017-Sep-06 18:12:03   Additional Information  Earth MOID = .609695 au   Jupiter MOID = .352027 au   T_jup = 2.605

Simulation in the past 

I used Mercury6 simulator by John Chambers to check what might have happened in the last 10^8 days (about 273000 years).

The arbitrary threshold for the ejection distance is 100 AU.

           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

I generated 100 clones with a little R script.

Every orbital parmeter has an average similar to the correspondent nominal one.

Every orbital parameter has a standard deviation equal to the uncertainty shown above.

Result of the simulation for the nominal orbit

These graphs were made using the R ggplot package.

Result of the simulation with 100 clones

After the simulation, I got 78 out of 100 clones that arrived from the outskirt of the solar system.

The actual arrival date range is extremely high: the most recent date was about 1565 AD.

The arrival date distribution is like this (time here is expressed in years):

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