Adam Hibberd
Yesterday I looked at another ‘Dark Comet’ – 2016 NJ33 to be precise. We have Doppler radar measurements of this object from Arecibo which have allowed Seligman et al to calculate an approximate diameter of 32 m.
As you may know I have a suspicion that many of these inner population ‘Dark Comets’ are defunct spacecraft mission hardware, like upper stages for example. Could this be the case for 2016 NJ33?
It turns out that its orbital inclination is around 6.6 degrees, which immediately makes it a bit of an outlier for human-launched space junk – only Zond 2 really conforms to this.
There is a problem though – 2016 NJ33 was nowhere near Earth when Zond 2 was launched. In fact when you look at the orbit of 2016 NJ33 going back hundreds of years we find ultimately that it had a resonant 2:3 orbit with the Earth (the ratio wasn’t just commensurate – this was definitely a resonant orbit). This would seem to make it very less-likely technogenic (human technology).
So what ON EARTH could it be? Some force must be causing those significantly non-zero Nongravitational Accelerations (NGAs) with NO VISIBLE OUTGASSING, the hallmark of a Dark Comet. I checked for the likelihood of these calculated NGAs being spurious, this turned out to be exceedingly unlikely.
Another strange feature of 2016 NJ33 is the DIRECTION of its NGAs – mainly radially outward from the Sun, but with a 5% tilt out of its orbital plane. The transverse component is negligible.
The whole thing is a mystery, especially as when you look at the MAGNITUDE of its NGA components, they are of a level expected by Solar Radiation Pressure as opposed to Yarkovsky. I dabbled with the notion of a technosignature, but I feel that may be a step too far. So work is on-going.