reported by meteordetective
Link to article which was updated on Thu 25-Feb-2016 at 14:40 Pacific Time (22:40Z) and was originally posted on Tue 02-Feb-2016.
NASA have refined their "earlier flyby and distance predictions, reconfirming that the asteroid poses no threat to Earth."
But, the 'plot' thickens, as NASA has additionally "..identified an extremely remote chance that this small asteroid could impact on Sep. 28, 2017, with odds of no more than 1-in-250-million. Flybys in 2046 and 2097 have an even lower probability of impact."
I thought I'd investigate further and used Telnet to 'talk' to JPL's "Horizons" system. However, as you can see (from the copy/paste below), there is no close-approach listed for 2017. To be clear and specific, I instructed Horizons to show me all the known approaches from 01-Jan-2000 to 01-Jan-2200.
Date (TDB) Body CA Dist MinDist MaxDist Vrel TCA3Sg Nsigs P_i/p
---------------------- ----- ------- ------- ------- ------ ------ ------ -------
A.D. 2001 Feb 12.30797 Venus .075550 .029997 .430225 10.352 95321. 27737. .000000
A.D. 2013 Oct 13.34047 Earth .013900 .013840 .013959 14.066 0.34 505.63 .000000
A.D. 2016 Mar 08.00436 Earth .033383 .000207 .115301 15.324 8719.4 463.31 .000000
A.D. 2024 May 21.93046 Mars .051950 .039661 .181328 15.950 8218.6 83319. .000000
A.D. 2028 Oct 22.29797 Earth .092654 .010847 .254975 11.643 36290. 37681. .000000
If you access the asteroid's entry in JPL's SBDB, you'll see the following Close-Approach dates & times listed, which barely correspond to the Telnet session results (above).
2016-Mar-08 00:06, 2056-Sep-18 13:29, 2071-Sep-30 14:02, 2074-Feb-17 05:44, 2084-Oct-20 19:33, 2086-Oct-16 07:11, 2089-Feb-07 09:03, 2089-Mar-14 21:35.
Is something out of sync?
I'd initially intended to comment on the wide variance of 2013 TX68's potential close-approach distances (all relative to Earth's surface), which are remarkable and summarised below:
Nominal (the expected or 'should be' distance): 13.06 LD = 3,099,296.455 miles
Minimum: 0.08LD = 15,282.762 miles
Maxium: 45.09LD = 10,714,428.346 miles
(For reference, 1 LD --aka 1 Lunar Distance-- is equivalent to 382,500 kilometers / 239,062.5 miles (NASA)).
The difference between minimum and maximum values is 7,615,132 miles or 8.19% of the distance from Earth to the Sun...or also equivalent to 3,185.42% the distance from Earth to the Moon....which is a rather large value.
To add a further variable in to this situation, MPC have assigned 2013 TX68 a condition code of 8 for its orbit uncertainty (10=highly uncertain and 0 = "good"), which is due to the fact that 2013 TX68 was only tracked for 3 days when it was initially discovered/observed - before it was 'lost' again.
Let me make myself perfectly clear: I'm not suggesting 2013 TX68 will hit Earth, inferring it or stirring-up 'fear-porn'. I'm just a little perplexed by the apparent of confusion --regarding when it will make its close-approaches to Earth-- and mentioning that there's a very wide margin of 'error' between the distances NASA are reporting for its 08-March-2016 close-approach.
Stay tuned!
Write to:
meteordetective AT gmail DOT com.
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