Late Discoveries

[bigmasterdrago]

It's sometimes interesting how we miss these small rocks until after closest approach. This appears to happen rather often. Take 2021 NU3 as an example, discovered just couple days ago, 1+ days after its close approach which occurred on July 8, 7:17UT (my location). The small (25') rock came in from the sun-ward side and directly over the north pole unseen at magnitude 15.7. It then continued outside our orbit and finally crossed the ecliptic a day later (9 July 3UT) at magnitude 17.6ish. At this point I think observations may have begun. It was actually a magnitude fainter when closest due to phase angle. At this point the orbit is still uncertain. Crazy stuff as sun-ward approaching rocks will surprise us.

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Some useful tools for getting info on rocks your interested in can be found at https://minorplanetcenter.net/db_search
and https://minorplanetcenter.net/db_search/...d=2021+NU3

And there, you can get a geocentric flyby diagram if you don't have software to do detailed solar system simulations. https://minorplanetcenter.net/neo/view?d...ig=K21N03U

[obrazell]

Like the Chelyabinsk object? That came from the sunward side and caused a bit of an issue when it hit.

[PMSchu]

Spotting these things after close approach is a fairly common occurrence, unfortunately. Anything coming from the sunward direction is naturally hard to spot. It usually misses & we can spot it, or it will never pass us again. If an asteroid explodes over the Pacific, does it make a sound? Sure does & sometimes our detectors can hear it.

The amazing ones are those that skip off the atmosphere & continue on.

Thanks for the web link BMD. It doesn't like the way I have MS Edge set up.

Phil S.