Moonlight, Twilight, or Daylight - 2022 GU6

[bigmasterdrago]

This big 100+ meter rock was first spotted April 9. It has been watched over 2 weeks with only 17 observations by Spacewatch, Pan-STARRS and Table Mountain. It appears to be heading for a close approach of ~3LD on ~June 12. For me, it will be out of range (16th mag). It also will have poor observing conditions as either moonlight, twilight, or daylight. Also, its phase % is poor. Thought it might be of interest to some for its size alone and recent discovery. Speed at close approach ~85"/sec moving thru Cepheus in the early morning hours of June 12.

[bigmasterdrago]

This rock needs to be watched carefully as the orbit uncertainty (now 8) will surely improve. Since this large rock is trailing behind us and only slightly above the ecliptic, the observations are only producing a very short, straight line. Not very good for orbit calculations. As it nears and catches up in late May, the orbit uncertainty will vastly improve. As it nears close approach (June 12), we should have much better, the ability to produce good ephemerides.

[PMSchu]

Hi BMD,

I saw this NEO listed on the CNEOS website yesterday, but the orbital elements weren't included in the MPC's NEAs at Today's Epoch data file yesterday. Today it's included. The ST4v ephemeris predicts a maximum brightness of 16.3 magnitude on Jun 12 @0400 EDT when it will be in Cepheus moving at 81.2"/min. When I calculate the ephemeris for these objects, I'm more interested in the maximum brightness than Min Re or motion across the sky, since if it's too faint, nothing else matters. Most of these objects tend to be fainter than 16 magnitude. 

It will be interesting to see if the predicted path changes much in the next few weeks. The Re is currently 0.2 AU, but it will come much closer. According to ST4v the current brightness is 21.5 magnitude in Coma Berenices.

Phil S.

[bigmasterdrago]

I got the els from Horizon/JPL and the other info from the MPC search page. I think after the 1st 4 obs, they realized it was near head on (or tail on) so the motion was so small that they waited until the 24 to resume obs. Kind of makes sense, I guess.

So often I've found that max mag does not occur at min dist, mostly due to the phase angle/%. so it behooves me/us to run an ephem for several days each side of close approach.

[PMSchu]

Hi BMD,

When I do the ephemeris calculations to screen for observable close approaches, I run the ephemeris for 40 days at 2-hour intervals. That seems to be good enough to find the time of maximum brightness. You're correct, max brightness usually doesn't coincide with Minimum Re due to the phase angle. It's similar to what happens with Venus.

I have no idea how close these predictions come to the actual brightness. Other than you, Dennis & George it doesn't seem like there are too many folks who try to observe these events, at least not on this forum.

Phil S.

[PMSchu]

The close approace of this NEO is almost here (max brightness on the morning of June 12 EDT). ST4v now predicts that the peak brightness will be 16.4 magnitude. Minimum Re is 1213.9k km (0.00808 AU) at 0800 EDT on June 12 when it will still be 16.4 magnitude moving through Cepheus at 85.1"/min. The ephemeris was calculated using the MPC's elements for NEAs at Today's Epoch for 2022 June 5 0000 UT.

The condidion code for the elements is now a '5' & the 'Rarity' for this approach remains a 2 according to the CNEOS website.

This object is just beyond the grasp of a 13" scope unfortunately.

Phil S.