Again on comet D/1770 L1 (Lexell)

Year 1757.

Three comets:

• D/1770 L1 (Lexell)
• P/2014 R5 (Lemmon-PANSTARRS)
• P/1999 RO28 (LONEOS)

Let's compare their nominal distance using JPL Horizons and Mercury6 software by John E. Chambers.

According to Mercury6 software, on 1757-Jul-1, the Lexell comet was at 0.33 (AU) from comet P/2014 R5 (Lemmon-PANSTARRS) and it was  at 0.16 (AU) from  comet P/1999 RO28 (LONEOS).

JPL Horizons models the Lexell comet in a different way.
According to JPL Horizons, the Lexell comet was at 1.53 (AU) from comet P/2014 R5 (Lemmon-PANSTARRS) and it was at 1.61 (AU) from  comet P/1999 RO28 (LONEOS).

Both JPL Horizons and Mercury agree and get the same result when looking  at the nominal distance between P/2014 R5 (Lemmon-PANSTARRS) and P/1999 RO28 (LONEOS).


Comet P/2014 R5 (Lemmon-PANSTARRS)

*******************************************************************************
JDCT 
   X     Y     Z
   VX    VY    VZ
   LT    RG    RR
*******************************************************************************
$$SOE
2362988.500000000 = A.D. 1757-Jul-17 00:00:00.0000 (CT)
  -5.257637317706235E+00  2.477814508385187E-01  6.790907841994050E-02
   1.426562748323473E-03 -5.796128684565190E-03  2.940516606550701E-05
   3.040181361915521E-02  5.263910851719347E+00 -1.697317088053800E-03
$$EOE
*******************************************************************************

Comet P/1999 RO28 (LONEOS)

*******************************************************************************
JDCT 
   X     Y     Z
   VX    VY    VZ
   LT    RG    RR
*******************************************************************************
$$SOE
2362988.500000000 = A.D. 1757-Jul-17 00:00:00.0000 (CT)
  -5.430809043797567E+00  3.084110607570195E-01 -7.118879844782251E-02
   2.327107819955809E-04 -4.558198020424996E-03  2.130564382053195E-03
   3.141896416246138E-02  5.440025008914496E+00 -5.186150467730436E-04
$$EOE
*******************************************************************************

Nominal distance (according to JPL Horizons): 0.23 (AU)
I get the same result using Mercury6 orbit simulator.

Given the orbit uncertainty that I am unable to evaluate, the idea that these comets are related is still a speculation.

I do not know if MPC should be involved in a case like this.

However, It would be nice to investigate this matter in a deeper way.


Kind Regards,
Alessandro Odasso