Divorced binary pair 2018 RY7 & 2017 SN16?

Rob D. Matson has identified a potentially recent divorced binary pair.

I tried to make a brief analysis simulating the likely past behaviour of this couple and for what it's worth, considering that the orbit uncertainty is still high, this is what I got.

Horizons Web Interface

(2018 RY7)

Classification: Apollo [NEO]          SPK-ID: 3829484

[ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Close-Approach Data ]

[ show orbit diagram ]

Orbital Elements at Epoch 2458200.5 (2018-Mar-23.0) TDB Reference: JPL 1 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .1467116969167884 0.0010984 a 1.01629583777152 0.00049788 au q .867193350842591 0.00089651 au i 13.35482024270498 0.11756 deg node 2.85350048046236 0.0074349 deg peri 137.0120977783837 0.1436 deg M 55.43317165629728 0.36927 deg tp 2458142.876998762314 (2018-Jan-24.37699876) 0.41734 TDB period 374.2214242076568 1.02 0.27499 0.0007529 d yr n .9619973008285991 0.00070692 deg/d Q 1.165398324700448 0.00057092 au

Orbit Determination Parameters    # obs. used (total)      26      data-arc span      2 days      first obs. used      2018-09-14      last obs. used      2018-09-16      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      7      fit RMS      .66894      data source      ORB      producer      Otto Matic      solution date      2018-Sep-16 16:12:15   Additional Information  Earth MOID = .0937949 au   Jupiter MOID = 3.83438 au   T_jup = 5.971

I generated 32 clones trying to achieve the same nominal parameters (and uncertainty): Clones Target mean sd mean sd q 0.86717277 0.00089801 0.86719335 0.00089651 e 0.14662991 0.00110031 0.1467117 0.0010984 i 13.33534837 0.11703745 13.35482024 0.11756 peri 137.01746383 0.14405351 137.01209778 0.1436 node 2.85228526 0.00740722 2.85350048 0.0074349 tp 2458142.86083199 0.41821974 2458142.87699876 0.41734 (2017 SN16) Classification: Apollo [NEO]          SPK-ID: 3781896 [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Close-Approach Data ] [ show orbit diagram ] Orbital Elements at Epoch 2458200.5 (2018-Mar-23.0) TDB Reference: JPL 10 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .1454600523472789 2.5667e-06 a 1.016120890077143 2.9297e-07 au q .8683158922153587 2.3652e-06 au i 13.38284125392155 0.0001647 deg node 2.763616636233115 6.2912e-05 deg peri 137.1159700228178 0.00015154 deg M 52.84406672421483 0.00029106 deg tp 2458145.582567069322 (2018-Jan-27.08256707) 0.00031821 TDB period 374.1247992555552 1.02 0.0001618 4.43e-07 d yr n .9622457552034478 4.1615e-07 deg/d Q 1.163925887938928 3.3558e-07 au Orbit Determination Parameters    # obs. used (total)      65      data-arc span      357 days      first obs. used      2017-09-24      last obs. used      2018-09-16      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      2      fit RMS      .40934      data source      ORB      producer      Otto Matic      solution date      2018-Sep-17 07:12:41   Additional Information  Earth MOID = .093169 au   Jupiter MOID = 3.83554 au   T_jup = 5.971  I generated 32 clones trying to achieve the same nominal parameters (and uncertainty): Clones Target mean sd mean sd q 0.8683155 2.37e-06 0.86831589 2.37e-06 e 0.14546049 2.58e-06 0.14546005 2.57e-06 i 13.38287471 0.00016469 13.38284125 0.0001647 peri 137.1160042 0.00015228 137.11597002 0.00015154 node 2.76363001 6.288e-05 2.76361664 6.291e-05 tp 2458145.58257208 0.00031662 2458145.58256707 0.00031821 Simulation The simulation has been made with MERCURY by 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. Algorithm Bulirsch-Stoer: )O+_06 Integration parameters  (WARNING: Do not delete this line!!) ) Lines beginning with `)' are ignored. )--------------------------------------------------------------------- ) Important integration parameters: )---------------------------------------------------------------------  algorithm (MVS, BS, BS2, RADAU, HYBRID etc) = BS  start time (days)= 2458200.5  stop time (days) = -1d8  output interval (days) = 100  timestep (days) = 0.05  accuracy parameter=1.d-12 )--------------------------------------------------------------------- ) Integration options: )---------------------------------------------------------------------  stop integration after a close encounter = no  allow collisions to occur = no  include collisional fragmentation = no  express time in days or years = years  express time relative to integration start time = no Note that the simulation was interrupted very early, i.e. around year 1840 A.D. Non gravitational effects have not been taken into account. Simulation Results I combined all 32 couples x 32 couples of clones, thus I got a total of 1024 couples. For every couple of clones, I looked for the time when they reached the minimum distance and I took note of their relative velocity as well. The interesting thing is that  many couples reached very low relative distances (less that 1 Lunar Distance). However, they did it with a relative high relative velocity. Looking at all couples, the "winning" one (i.e. the couple that reached the minimum distance) behaved like this apparently around 1840 A.D.: Of course, going back in the past even more ... , a similar pattern occurs. Kind Regards, Alessandro Odasso