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 2016 TS54 - Simulation: one hyperbolic clone

11.Nov.2017 - Thanks to Marshall Eubanks for replying to my post.

===========================================
Original post:

This is an Apollo asteroid and a NEO.
The orbit uncertainty is very high (condition code 7).

JPL data:

(2016 TS54)

Classification: Apollo [NEO]          SPK-ID: 3760683

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

[ show orbit diagram ]

Orbital Elements at Epoch 2458000.5 (2017-Sep-04.0) TDB Reference: JPL 3 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .6765980973308807 0.00042289 a 2.468718466581417 0.0029955 au q .7983882492468207 7.6008e-05 au i 6.14907656306426 0.0027978 deg node 16.99108750103253 0.00070824 deg peri 300.2822592251591 0.0016973 deg M 93.48517533503207 0.17205 deg tp 2457632.586247835889 (2016-Sep-01.08624784) 0.0074744 JED period 1416.790954334841 3.88 2.5787 0.00706 d yr n .2540953546453251 0.00046247 deg/d Q 4.139048683916013 0.0050223 au

Orbit Determination Parameters    # obs. used (total)      32      data-arc span      3 days      first obs. used      2016-10-11      last obs. used      2016-10-14      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      7      fit RMS      .49696      data source      ORB      producer      Otto Matic      solution date      2017-Apr-06 08:23:07   Additional Information  Earth MOID = 4.26889E-5 au   Jupiter MOID = 1.25134 au   T_jup = 3.116

Just for fun, I simulated 100 clones of this Apollo asteroid in the past 10^8 days trying to see if there are signs of a possible cometary origin:
i.e. whether some clones might have arrived from the outskirt of the solar system - 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

The cometary origin of Asteroid 2016 TS54 is less clear than in other cases where I got a lot of clones with cometary-like orbits.

Anyway, in this case 9 out of 100 clones arrived in the solar system from a distance greater than 100 AU.

I would not be surprised if many more clones would get ejected if the simulation went more back in the past.

> summary(ejected$Year):

   Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
-276671 -243932 -219308 -221057 -202058 -141985

This plot shows the distribution time in a graphical way:

One thing that sometimes occurr during these simulations ... many clones that had to be discarded - because they seem to have originated from the sun due to a very high eccentricity:

From file.out of Mercury simulator:
  was hit by TS_94    at     -35503 11  8.1
  was hit by TS_47    at     -54568  9 14.4
  was hit by TS_98    at     -99015 10 20.5
  was hit by TS_72    at     -99560  2 21.8
  was hit by TS_96    at    -148788 10  6.0
  was hit by TS_91    at    -149964 11 28.2
  was hit by TS_7     at    -156722  2  4.0
  was hit by TS_77    at    -162338  5 30.9
  was hit by TS_73    at    -166169  2 21.5
  was hit by TS_9     at    -168018 11 11.8
  was hit by TS_18    at    -191284  7 16.3
  was hit by TS_48    at    -200641 11 13.5
  was hit by TS_8     at    -207786  9 27.0
  was hit by TS_51    at    -217189 12 14.4



A curious clone - hyperbolic orbit
What is curious is that one clone (only one!) seems to have entered the solar system following an hyperbolic trajectory.


Day             a        e      i        w       om
...
...
-99309899.5 -61.47015 1.111092 2.6958 241.4296 241.5559
-99309799.5 -61.48959 1.111059 2.6970 241.4380 241.5471
-99309699.5 -61.41541 1.111200 2.6980 241.4380 241.5401
-99309599.5 -61.29102 1.111422 2.6994 241.4445 241.5318
-99309499.5 -61.07459 1.111812 2.7014 241.4495 241.5226
-99309399.5 -60.62682 1.112621 2.7044 241.4565 241.5127
-99309299.5 -59.72419 1.114282 2.7101 241.4700 241.5018
-99309199.5 -57.25347 1.119078 2.7246 241.5052 241.4958
-99309099.5 -36.49813 1.182189 2.7886 242.9846 241.5639


Then, there was an encounter with Saturn:



Days Planet       Dmin        a1       e1    i1
-99309089 SATURN 0.02332127 -402.1809 1.013726 0.314 

The encounter distance was 0.02 AU, the semi-major axis had a spike ...physically possible or not? (I do not know!) but the clone was then captured in an elliptical orbit:

After the encounter we see:

Day             a        e      i        w       om
-99308999.5  28.48699 0.812484 1.3768  71.9542  78.5563
-99308899.5  27.76675 0.807261 1.3830  71.9916  78.5274
-99308799.5  27.55270 0.805645 1.3842  71.9835  78.5263
-99308699.5  27.45602 0.804901 1.3846  71.9719  78.5273
-99308599.5  27.40985 0.804531 1.3848  71.9557  78.5286
-99308499.5  27.39724 0.804417 1.3849  71.9409  78.5301
-99308399.5  27.38719 0.804331 1.3850  71.9305  78.5308
-99308299.5  27.39765 0.804393 1.3850  71.9164  78.5324
 ....

I think this is just a simulation fluke due to the fact that clones "diverge" quite a lot and so some of them seem to have an hyperbolic trajectory.

However, this raises a question: people who are really expert in this field may be able to put some constraint about the probability of these "unstable" asteroids (or old comets?) being hidden interstellar objects captured a long time ago.

This possibility is related to the question "how rare is a close passage of an interstellar rock to our star?" discussed by Alan Harris in this MPML message.

This analysis would be interesting considering the very recent discovery of the first recognized interstellar object by Robert Weryk on October 19, 2017 with observations made by the Pan-STARRS telescope:

A/2017 U1 = 1I/'Oumuamua (MPEC 2017-V17)

A few nice links about this discovery (impossible to give all ... but I share with you the ones that most impressed me):

• the "early warning" given by Bill Gray, probably the first public mention!

• A deep analysis from Bill Gray that summarizes why the object is with no doubt interstellar (in response to many questions, including mine,  on whether there might be alternative explanations).

•  images of the objects taken by Paolo Bacci and Martina Maestripieri

• A simulation from Tony Dunn 

• look at MPML to see very interesting threads about this object.

Kind Regards,
Alessandro Odasso

asteroid 2016 WU9 vs comet 3D/Biela

Comet 3D/Biela was a Jupiter Family comet discovered in 1772 by Montaigne and, independentely, by Messier. 

It was identified as periodic in 1826 by Wilhelm Van Biela (period 6.6 years).

In the following decades, the comet disintegrated and in 1872, quoting Wikipedia , "...a brilliant meteor shower (3,000 per hour) was observed radiating from the part of the sky where the comet had been predicted to cross in September 1872. This was the date when Earth intersected the comet's trajectory. These meteors became known as the Andromedids or "Bielids" and it seems apparent that they were produced by the breakup of the comet. The meteors were seen again on subsequent occasions for the rest of the 19th century, but have now faded away, probably due to gravitational disruption of the main filaments".

Looking at JPL Small-Body Database Browser, it seems that the current Apollo asteroid 2016 WU9 orbit bears some resemblance with the orbit of comet 3D/Biela (orbital element estimated at epoch 1832-Dec-03.0).

3D/Biela

Classification: Jupiter-family Comet [NEO]          SPK-ID: 1000504

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

[ show orbit diagram ]

alternate orbits:

Orbital Elements at Epoch 2390520.5 (1832-Dec-03.0) TDB Reference: IAUCAT03 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e 0.751299 n/a a 3.53465808340135 n/a au q 0.879073 n/a au i 13.2164 n/a deg node 250.669 n/a deg peri 221.6588 n/a deg M .9469569963959761 n/a deg tp 2390514.115200000000 (1832-Nov-26.61520000) n/a JED period 2427.278122182916 6.65 n/a n/a d yr n .1483142770949718 n/a deg/d Q 6.190243166802708 n/a au Additional Model Parameters  Parameter Value Uncertainty (1-sigma)  A1 [SET] 0.39E-8 n/a A2 [SET] -0.0254E-8 n/a		Orbit Determination Parameters    # obs. used (total)      26      planetary ephem.      DE405      data source      ORB      producer      Marsden   Additional Information  Earth MOID = .000518224 au   T_jup = 2.531

(2016 WU9)

Classification: Apollo [NEO]          SPK-ID: 3764861

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

[ show orbit diagram ]

Orbital Elements at Epoch 2457719.5 (2016-Nov-27.0) TDB Reference: JPL 3 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .7580579821266318 0.0032624 a 3.542266282670314 0.046712 au q .8570230522740508 0.00025535 au i 11.74490053832628 0.036722 deg node 243.8119317636647 0.0028055 deg peri 238.6437633713563 0.0047637 deg M 354.0963591324415 0.12305 deg tp 2457759.433526534912 (2017-Jan-05.93352654) 0.042468 JED period 2435.119255232367 6.67 48.168 0.1319 d yr n .1478367021354146 0.0029243 deg/d Q 6.227509513066578 0.082122 au

Orbit Determination Parameters    # obs. used (total)      14      data-arc span      5 days      first obs. used      2016-11-26      last obs. used      2016-12-01      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      8      fit RMS      .57283      data source      ORB      producer      Otto Matic      solution date      2017-Apr-06 08:21:48   Additional Information  Earth MOID = .0396698 au   Jupiter MOID = .640753 au   T_jup = 2.523

One can wonder whether asteroid 2016 WU9 is a remnant of comet 3D/Biela.

In order to answer, it would be important to be able to model the effect of non gravitational forces.

I am unable to do that but I show you the result of a simulation done with Mercury6 taking into account only gravitational forces.

Simulation set-up

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

In order to perform the simulation I generated 100 clones of asteroid 2016 WU9 (same average orbital parameters as the nominal ones and standard deviation almost about the one calculated by JPL).

I also simulated the behavior of nominal comet 3D/Biela for which I do not find the uncertainty estimates.

Thus, I evaluated 100 couples with an R script to check whether there was a moment in the past when two clones were very near to comet 3D/Biela with a very low relative velocity.

Simulation Results
First, you see a graph showing the relative distance between 2016 WU9 clones and come 3D/Biela (some outliers not shown).
Second, the correspondent graph for relative velocities.

At first glance nothing impressive but around January 1806, one clone and nominal comet D/Biela were separated by a distance of about 10 LD (i.e.  0.025 AU) with a relative velocity 0.0030 AU/Day.
For comparison: I read that in 1852  two fragments comet A and comet B were observed and their distance was estimated to be about 2.5 million km (i.e 6 LD).
In conclusion:

• for a few clones, the order of magnitude of the distance may be compatible with 2016 WU9 being a fragment of the comet.

Not clear to me if this is just a coincidence or there could be more.

2016 WU9 - a possible cometary origin
While the relation between asteroid 2016 WU9 and comet 3D/Biela remains highly speculative, I think it is interesting to note a second result of the simulation of asteroid 2016 WU9: this Apollo asteroid seems to move on an unstable orbit, it might have a cometary origin itself (whether or not it is related to comet 3D/Biela).

Of course, the uncertainty is very high, but, at least, this result is consistent with the fact that asteroid 2006 WU9 appears in the  Asteroids with Comet-Like Orbits: Elements and Positions by Fernandez.
This is what I got (graph done with package ggplot2):

• 68 out of 100 clones arrived in the solar system from a distance greater than 100 AU
• 4 out of 100 clones "hit" the sun (considering that the integration was backword, this means that they seem to have originated from the sun - not clear if this is a simulation glitch or a "normal" result that happens when the eccentricity gets almost 1)

Arrival Time distribution

Year of clone arrival time :

     Min.   1st Qu.    Median      Mean   3rd Qu.      Max.
-271250.0 -158468.8  -79389.5 -103213.8  -40550.2     -32.0  

In a graphical form:

Every clone has its own story, no reason to choose a specific one.
Just to have a feeling of a possible macroscopic behaviour (the dotte lines correspond to a close encounter with Jupiter):

Kind Regards,
Alessandro Odasso