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Francesco Manca has pointed out on MPML that this very small object, discovered at Mt. Lemmon on Sept 18, will make a very close approach to the Earth on September 24.45. The object is less than 10m in diameter. I tried to get it last night, but it was around mag 21 then and my transparency was poor so I didn’t get it. It was then around 2.2 million km away. Tonight it will be brighter (mag 20.4) and Monday night it will be 19.7. The motion is quite slow (<2.5 arcsec/min) since it is heading almost straight for us and it is conveniently placed in the Square of Pegasus. The motion increases rapidly from the night of 22/23 Sept and the magnitude also brightens rapidly. At 0h UT on Sept 24 it will be 16th mag moving at 42″/min. Closest approach, when it is within 30,000 km of the Earth’s centre, is not visible from the UK but it could reach mag 13 although it would then be moving at a rate of a degree every couple of minutes!
The attached ephemeris is based on a short arc and the position uncertainties are growing so astrometry over the next couple of nights would be useful if you can go that faint.
Nick.
I managed to get some astrometry of this very small object this evening and it was a bit off track. An updated ephemeris is attached. Tonight it is around 19.7, tomorrow night (Tuesday) it will be 18.6 moving at 5″/min and Wednesday night it will be up to 16th mag but accelerating through 30″/min. It then moves rapidly south and we lose it as it comes within the geostationary satellite belt for a short period around Sept 24.45.
Note the ephemeris is for my location and the position will be different for you. This will become more significant the further from Essex you are and the closer the object gets. Let me know if you want an ephemeris for your location.
The attached are updated elements of 2020 SW including my astrometry from last night. These should help if you are using any program which uses the MPC elements. This is actually a text file but for some reason you can’t upload those.
Managed to catch it around midnight during a brief clear very transparent slot following the swirl of cloud that caused such heavy rain yesterday afternoon. The coldest night of the autumn here so far. Was 4C by the time I closed down – must bring the geraniums indoors.
I caught it between 22:01h -22:23h UT last night with a C8. Cropped 39x30s sequence here:
https://www.youtube.com/watch?v=AZLNgdQheto&feature=youtu.be
David
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