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

Asteroid 2017 YE5 - binary object with cometary origin?

This is an interesting asteroid discovered by the Morocco Oukaimeden Sky Survey on Dec. 21, 2017

This asteroid is an Apollo and PHA and immediately following its discovery it was suspected to have a cometary origin.

In June 2018, observations from NASA's Goldstone Solar System Radar showed that the asteroid could be a binary system and this was confirmed by the Arecibo Observatory in Puerto Rico and the Green Bank Observatory in West Virginia.

There are two questions:

• how likely is this object to have a cometary origin based solely on its current orbital parameters and uncertainty?
• is its  binary nature telling us something about its origin? is it more likely to have a cometary origin or not?

I tried myself to answer in a rough way the first question and I  am looking forward to reading the first scientific results regarding the second question.

Regarding the cometary origin, as a first step, I read data from JPL Small-Body Database Browser and I generated 100 clones to simulate their behaviour in the last 1e8 JD.

(2017 YE5)

Classification: Apollo [NEO, PHA]          SPK-ID: 3795078

[ 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 38 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .7102764889674997 2.4274e-06 a 2.820304229389295 2.1688e-05 au q .8171084435184766 5.6341e-07 au i 6.209783873125096 2.5738e-05 deg node 103.960295639342 1.8222e-05 deg peri 110.7683468906294 3.1019e-05 deg M 348.9948146835015 0.00012049 deg tp 2458253.385574217192 (2018-May-14.88557422) 3.1167e-05 JED period 1729.985108896518 4.74 0.019956 5.464e-05 d yr n .2080942767360745 2.4004e-06 deg/d Q 4.823500015260113 3.7093e-05 au

Orbit Determination Parameters    # obs. used (total)      292      data-arc span      213 days      first obs. used      2017-12-12      last obs. used      2018-07-13      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      4      fit RMS      .32615      data source      ORB      producer      Otto Matic      solution date      2018-Jul-14 06:51:38   Additional Information  Earth MOID = .0205924 au   Jupiter MOID = .420057 au   T_jup = 2.875

Clone generation

I tried to generate clones that have the same orbital parameters (mean and sigma) shown above.

This table summarizes what has been achieved versus the intended nominal target:

	clones_mean	clones_sd	target_mean	target_sd
q	0.81710847	5.6E-07	0.81710844	5.6E-07
e	0.71027634	2.43E-06	0.71027649	2.43E-06
i	6.20978289	2.6E−05	6.20978387	2.6E−05
peri	110.76834516	3.1E−05	110.76834689	3.1E−05
node	103.96029755	1.82E-05	103.96029564	1.8E−05
tp	2458253.38557146	3.1E−05	2458253.38557422	3.1E−05

Simulation Algorithm

Mercury 6 integrator by John Chambers  (1999): "A Hybrid Symplectic Integrator that Permits Close Encounters between Massive Bodies''. 

Monthly Notices of the Royal Astronomical Society, vol 304, pp793-799.

I used the general Bulirsch-Stoer algorithm with all planets from Mercury to Pluto plus asteroids Ceres, Pallas and Vesta.

I also used as usual an arbitrary threshold of 100 AU as ejection distance from the solar system.

)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
)---------------------------------------------------------------------
ejection distance (AU)= 100
radius of central body (AU) = 0.005
central mass (solar) = 1.0

Graphic tools
All plots below have been implemented in language R using the package ggplot2.

  R Core Team (2018). R: A language and environment for statistical
  computing. R Foundation for Statistical Computing, Vienna, Austria.
  URL https://www.R-project.org/.

Simulation Results
About 60% of the clones were ejected from the solar system in this backward simulation (i.e. they actually came from the outskirt of the solar system and they have a likely cometary origin).

This plot shows that the numer of clones is initially 100 and then as you go back in the past (from right to left) their number is decreasing due to ejection from the solar system:

This second plot below shows the density distribution of the arrival time in the solar system:

In the following plots the simulation time has been divided into 10 slots and for every slot we show the distribution of the maximum parameter achieved in that time slot by all clones (their number is shown in red):

Specific Energy

In this plot, by definition, a specific energy greater than 0 means clones travelling on a hyperbolic trajectory:

The hyperbolic clones had the following V-Infinity:

Orbital Period

Eccentricity

Inclination

Peri

ascending node

Footprint q-Q
We can get rid of the temporal dimension and plot the density graph showing where the clones (only those on elliptical orbits) have been most of the time in the plane q-Q:

 

Footprint e-i

same approach as above:

Footprint w-om

Analysis of close approaches

Kind Regards,
Alessandro Odasso

Asteroid 2016 BS30 = 2010 HD50 - Cometary origin?

Horizon Web data
(2016 BS30)

Classification: Outer Main-belt Asteroid          SPK-ID: 3743356

[ 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 9 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .3478863638049197 7.7899e-07 a 3.820502999526835 7.8608e-07 au q 2.491402103115656 3.4304e-06 au i 11.67728524676726 7.6434e-05 deg node 326.2245320214484 9.1269e-05 deg peri 245.4466373090264 0.00026973 deg M 60.18000341810182 0.00025871 deg tp 2457744.537683238532 (2016-Dec-22.03768324) 0.0018283 JED period 2727.590972265617 7.47 0.00084182 2.305e-06 d yr n .1319845987395147 4.0734e-08 deg/d Q 5.149603895938015 1.0596e-06 au

Orbit Determination Parameters    # obs. used (total)      54      data-arc span      4641 days (12.71 yr)      first obs. used      2003-08-26      last obs. used      2016-05-10      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      1      fit RMS      .55107      data source      ORB      producer      Otto Matic      solution date      2018-Jul-09 06:23:30   Additional Information  Earth MOID = 1.51491 au   Jupiter MOID = .65024 au   T_jup = 2.935

Clones generation

I generated 100 clones trying to achieve the same orbital parameter distribution as shown above (mean and sigma).

This is a table comparing what has been achieved versus the target:

	clones_mean	clones_sd	target_mean	target_sd
q	2.4914019	0.0000034	2.4914021	0.0000034
e	0.3478864	0.0000008	0.3478864	0.0000008
i	11.6772762	0.0000767	11.6772853	0.0000764
peri	245.4466251	0.0002691	245.4466373	0.0002697
node	326.2245392	0.0000916	326.2245320	0.0000913
tp	2457744.5376278	0.0018291	2457744.5376832	0.0018283

Backward simulation
I used the Bulirsch-Stoer algorithm implemented by the Mercury software 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.


           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

   Includes collisions:                 no
   Includes fragmentation:              no
   Includes relativity:                 no

The arbitrary threshold to consider an asteroid to be ejected from the solar system (or to enter it in case of backward simulation) is 100 au.

All planets from Mercury to Pluto plus asteroids Ceres, Pallas and Vesta have been taken into account.

Simulation results
76 out of 100 initial clones have entered the solar system from a distance greater than 100 au.

The graph below has to be read from right to left (the number of clones decreases as you go in the past - the simulation time has been divided into 10 intervals).

The arrival time into the solar system has the following density distribution:

In the following graphs, the simulation time has been divided into 10 intervals: in every interval and for every clone we find the maximum value for the relevant orbital parameter.

Orbit Specific Energy

Some clones were on a hyperbolic orbit with the following v-infinity:

Orbit eccentricity

Orbit Inclination

Analysis of Close Approaches

Kind Regards,
Alessandro Odasso

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

Just for curiosity, the distribution of V-infinity for the 7 hyperbolic clones is as follows:

Inclination

Eccentricity

Kind Regards,
Alessandro Odasso