174P/Echeclus

60558 Echeclus (2000 EC98) also known as 174P/Echeclus is a centaur that occasionally shows a cometary activity.

Outbursts happened in 2005, 2011 and in the first days of December 2017 (see MPML message from Brian Skiff) and confirmation from Richard Miles and Jean-François Soulier.

The 2017 outburst is the strongest ever witnessed.

I simulated 100 clones of this centaur in the past 10^8 days trying to confirm its possible cometary origin: note that I am not taking into account the non gravitational forces associated to its outburst, not clear to me if they have a considerable effect.

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

JPL Small-Body Database Browser

60558 Echeclus (2000 EC98)

Classification: Centaur          SPK-ID: 2060558

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

[ show orbit diagram ]

Orbital Elements at Epoch 2458000.5 (2017-Sep-04.0) TDB Reference: JPL 85 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .4556668817376728 1.2005e-07 a 10.68172886788859 2.2774e-06 au q 5.814418783090517 4.1275e-07 au i 4.344445692331014 6.4394e-06 deg node 173.3332131350017 5.505e-05 deg peri 162.8042218299513 5.7268e-05 deg M 24.47205469604485 6.4974e-06 deg tp 2457133.680473384613 (2015-Apr-21.18047338) 0.00022632 JED period 12751.48464064088 34.91 0.004078 1.116e-05 d yr n .02823200671493785 9.0289e-09 deg/d Q 15.54903895268667 3.3152e-06 au

Orbit Determination Parameters    # obs. used (total)      2888      data-arc span      13948 days (38.19 yr)      first obs. used      1979-09-23      last obs. used      2017-11-30      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      0      fit RMS      .44363      data source      ORB      producer      Otto Matic      solution date      2017-Dec-07 16:00:47   Additional Information  Earth MOID = 4.80483 au   Jupiter MOID = .838614 au   T_jup = 3.031

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 (general)

   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

• 77 out of 100 clones have a cometary orbit (i.e. they came from a distance greater than 100 AU).

• of which: 3 came on a hyperbolic orbit. The one that had the highest speed had a Vinfinity about 3.7 km/s (Vinfinity = 42.1219*sqrt(-0.5/a) --> the semi-major axis being about -63.6 AU

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

   Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
-272080 -109330  -62183  -82802  -36357   -4980

In a graphical form:

A look at the nominal asteroid
The nominal asteroid itself has a cometary origin.

It entered into the solar system at about year -105000 B.C.

In the plot below, the dashed vertical lines correspond to a close approach with Jupiter.

Note that Jupiter was not immediately important. 

In its early history, 174P/Echeclus was much more influenced by Saturn as shown here:

Coming back to plots showing the role of Jupiter, we can see these other ones:

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 - color scale implemented by viridis library):

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

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:

JPL Small-Body Database Browser

 

(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 (2016-Oct-06.29475008) 0.0066681 JED period 3079.781063466159 8.43 1.6825 0.004606 d yr 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

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

• 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

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