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2010 CA261 Close approach
I'm trying to determine where the elements came from that have the H=16.6 as all the sources I've been able to resource have it at H=99.99.
Hi All,

This is a weird object that I found using the DBPS after updating the MPC elements for NEAs at Today's Epoch today. It's very bright & now moving retrograde WRT earth at 0.03 AU. The mag is currently 10.8, but ST4v estimates it will brighten to 9.5 mag between Sep 3-10 as we overtake it. It's not moving very fast & its orbit is close to earth's.

Might be worth a look if anyone's interested. I'm surprised it didn't appear in previous DBPS searches. It's also not listed on the CNEOS page at JPL.

Good hunting,

Phil S.
The OI for this object says it's 1-3 km, the eccentricity is 0.04 & the inclination is 0°. I went to HORIZONS & ran the motion for several years. I keeps realigning with earth every year, it's odd that it wasn't picked up again between 2010 & now.

Just strange. I couldn't image it. Aliens  Wink?

Phil S.
What is OI? 1-3Km!!. Must be a Black Hole Confused

Or a danged black rock.

OI stands for ST4v's Object Information dialog. If you have the data for 2010 CA261 in an Observing List (OL), open the OI dialog & see what it says for the size. Is 2010 CA261 in your MP database? If so how did you get that data?

Very challenging object. I'm learning a lot. I need to load some of the images into to see where the image center is located. My .fits file headers don't include that info, unfortunately so ST4v couldn't put an image into the IA.

Phil S.
Completely agree on the oddity of no recovery in 11 years, looks like a captured asteroid in the orbital simulation. As I mentioned in the other post, discovered by WISE so no magnitude. Maybe just a single passing small rock that is lost and all the elements and orbit info is completely wrong with the short, straight line 27 hour observation.

Thanks for the definition of OI = right click in the IA, select OI.

I did a single minor planet download and also used Horizons for specific times of Osculating Elements. It's also in the Lowell data for use in other software.
Finally figured out the field for the images on 2021 Aug 15 @0300 from T16. There is no object at the calculated position of 2010 CA261. Stars to mag ~15.5 are recorded in the image. Either the position is wrong or the mag estimate is way off. Hard to believe a 1-3 KM object keeps coming this close to earth (0.03 AU) every year & it doesn't make the news.

Sorry for the false alarm, but I did learn a lot from the exercise.

Phil S.
I was taking another look at this object and did a fresh download. The MPCORB lists it as an Apollo but when downloaded using the MPC NEA Today, shows as an Aten. When I look it up at the Minor Planet Center Info Search, it shows as an Apollo. I had to do some investigating as it appears this object is both an Apollo and Aten if we take their definitions at face value as it does not spend most of its time inside or outside our orbit. It's almost 50/50 being outside Earths orbit from June 30 to December 19 and inside the rest of the time. Crazy object. The orbit view is from directly above the barycenter. Again, the end of the month and into early September may be a good time to make another attempt to hunt for this little strange object.

Clear skies,
Head Dude at Skyhound
I tried to image 2010 CA261 using both T08 & T32 at Siding Spring, Australia on the morning of 2021 Aug 18. Nothing appears at the predicted position. Stars were recorded to fainter than 16.5 magnitude. The prediction is for 10.5 at that time.

Try running the motion into the future & watch it realign with the earth every year. If the H value of 16.6 is picked up as a default, then the mag estimates aren't reliable. The ST4v estimate of 1-3 km is certainly suspect.

Interesting is an understatement, Greg. As Spock would say, "Fascinating!"

Phil S.
I understand that asteroids do occasionally change their category as a result of orbital changes, but this is the only one that I've run across that is a good example.

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