Blog Archive

Monday, December 4, 2017

Amor (Neo) 2017 BR93

This NEO is listed in the page of Asteroids with Comet-Like Orbits maintained by Y. Fernandez.

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.

The first step was to generate clones having orbital parameters distributed around the nominal ones with 1-sigma uncertainty as follows:

(2017 BR93)

Classification: Amor [NEO]          SPK-ID: 3767926
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 5 (heliocentric ecliptic J2000)
 Element Value Uncertainty (1-sigma)   Units 
e .7217412317070279 0.0001002
a 4.142675777273991 0.0015088 au
q 1.152735859221392 3.3533e-05 au
i 15.35366999553024 0.001219 deg
node 97.57957971696266 0.0028893 deg
peri 318.8120872155768 0.0036121 deg
M 38.89039107061564 0.021706 deg
tp 2457667.794750083124
0.0066681 JED
period 3079.781063466159
n .1168914259102677 6.3858e-05 deg/d
Q 7.13261569532659 0.0025977 au
Orbit Determination Parameters
   # obs. used (total)      34  
   data-arc span      75 days  
   first obs. used      2016-11-23  
   last obs. used      2017-02-06  
   planetary ephem.      DE431  
   SB-pert. ephem.      SB431-N16  
   condition code      6  
   fit RMS      .44498  
   data source      ORB  
   producer      Otto Matic  
   solution date      2017-Nov-30 06:50:30  

Additional Information
 Earth MOID = .222957 au 
 Jupiter MOID = .227161 au 
 T_jup = 2.447 

The orbit condition code is 6 so there is still a lot of uncertainty.

Simulation approach

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
  • 75 out of 100 clones have a cometary like orbit.
    • of which: 16 came on a hyperbolic orbit. The one that had the highest speed had a Vinfinity about 15.2 km/s (Vinfinity = 42.1219*sqrt(-0.5/a) --> the semi-major axis being about -3.82 AU

The time (Year) when they entered the solar system was distributed as follows:

   Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
-276249 -148774  -75459  -98680  -33904    -709

In a graphical form:

A look at the nominal asteroid
The nominal asteroid itself does not have a cometary origin in the last 10^8 days. It appears to be nevertheless on a unstable orbit, there was a time in the past when its aphelion was at about 70 AU.

In the following plots (made with R package ggplot2), the vertical dashed lines show a close encounter with Jupiter.

A look at the clones - "footprint" diagrams
At any given time in the past, a clone had a certain perihelium q and a certain aphelium Q (I disregard the clones when on an hyperbolic trajectory because Q would be infinite).
Let's imagine that we plot all possible q-Q points in a diagram: the highest density area is the one where the clones happened to be for most of the time.

This is shown here ( I have used the R function stat_density2d):

In the diagram above, we can also see the current q-Q of the asteroid together with that of Jupiter and Saturn.
In a similar way, these are the footprints for w-om and e-i:

Analysis of close approaches
These plots show the distribution of close appproaches (number and Dmin distance) between the clones and the major planets.

Kind Regards,
Alessandro Odasso

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.