astro: 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

[ 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
t_p	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

[ 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
t_p	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.