[neo_followup] C3X8FH2, likely fragment of 2014 WJ6, whizzes by Earth

[Sam Deen]

Hi all,

A pretty interesting TJ<3 looking object was added to the NEOCP earlier today, found by MLS with a 2 hour observation arc. Ultimately any orbit with an arc measured in hours is going to not be very robust, but this one passed close enough to us (58,000 +/- 10,000 km) that you can get a decent enough idea of it. Nominally it's this:

   Perihelion 2020 Oct 10.698938 +/- 1.61 TT = 16:46:28 (JD 2459133.198938)
Epoch 2020 Nov 15.0 TT = JDT 2459168.5   Earth MOID: 0.0000   Ju: 0.6612
M   6.80577660 +/- 4.6              (J2000 ecliptic)          Find_Orb
n   0.19279240 +/- 0.133            Peri.  126.60087 +/- 0.6
a   2.96762782 +/- 1.37             Node   232.43714 +/- 0.047
e   0.7231549 +/- 0.133             Incl.    6.23886 +/- 0.8
P   5.11                   H 31.2   G  0.15   U 11.4  
q 0.82157312 +/- 0.021    Q 5.11368252 +/- 3.58
>From 7 observations 2020 Nov. 15 (1.9 hr); mean residual 0".37

Which puts it as a surprisingly small jupiter-crossing asteroid. In fact, if the nominal orbit is true, it would be the only H>30 object ever discovered with an aphelion beyond 5 AU. The chances of recovery aren't too big at the moment though- because of its small size and understandably high velocity, it's already at magnitude 22-23 with an uncertainty of several arcminutes, so unless someone somehow manages to snap the CFHT around on it tonight, this seems to be all the data we're going to get.

Fortunately, I don't think we need a lot more data. Out of curiosity, I performed a search of other asteroids on similar orbits and turned up a surprisingly robust match: 2014 WJ6, an H=27.1 asteroid on a similar enough orbit that I feel confident suggesting that C3X8FH2 is a tiny fragment of it, maybe even a divorced binary- even with the uncertainty in its exact eccentricity.

https://i.imgur.com/zzC5F8S.png

I wonder if there are any other associated asteroids with sizes this small...

~Sam