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Thursday, October 26, 2017

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).


Classification: Jupiter-family Comet [NEO]          SPK-ID: 1000504
Ephemeris | Orbit Diagram | Orbital Elements | Physical Parameters | Discovery Circumstances ]

[ show orbit diagram ]

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
n/a JED
period 2427.278122182916
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
0.042468 JED
period 2435.119255232367
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

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

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