Talk:4581 Asclepius

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Was the near-collision date Mar 22 or Mar 23? This page currently says Mar 22, but the below page says Mar 23 http://en.wikipedia.org/wiki/Asteroid_deflection_strategies#1989

The 22nd. I fixed it. Saros136 (talk) 02:50, 28 March 2008 (UTC)

The surface temperature seeems REALLY too cold for me. Both in Celsius and, even worst, in Kelvin. (unnamed user 04:42 UTC 30 Sept 2007)

Actually, 275 Kelvins is 2 Celsius, or 36 Fahrenheit. Chilly, but livable with a jacket. Just stay indoors there or in your space suit. GBC (talk) 10:02, 12 August 2008 (UTC)

Could add

Content copied from near-earth asteroid :

On March 23, 1989 the 300 meter (1,000-foot) diameter Apollo asteroid 4581 Asclepius (1989 FC) missed the Earth by 700,000 kilometers (400,000 miles) passing through the exact position where the Earth was only 6 hours before. If the asteroid had impacted it would have created the largest explosion in recorded history, thousands of times more powerful than the Tsar Bomba. It attracted widespread attention as early calculations had its passage being as close as 40,000 miles from the Earth, with large uncertainties that allowed for the possibility of it striking the Earth.

Could add to this article Rod57 (talk) 16:30, 9 October 2008 (UTC)

References

Units

personally, i prefer AU, but i see Gm used pretty consistently on similar pages. one thing's for sure: megametre is not the way to go.

also, i think megajoule is better than kiloton-TNT-equivalent. —Preceding unsigned comment added by Peterhoneyman (talk • contribs) 00:33, 8 May 2010 (UTC)

Minimum/maximum possible distance

The minimum and maximum possible distances of JPL are misnamed. The JPL Horizons page say, with close-approach results,

IMPORTANT NOTE:

All tabulated statistical quantities (MinDist, MaxDist, TCA3Sg, Nsigs and P_i/p) are based on a linearized covariance mapping in which higher-order (small) terms in the variational partial derivatives of the equations of motion are dropped.

Due to possible non-linearities in any given object's actual dynamics, this can result in significant errors at epochs distant in time from the solution epoch.  Consequently, long linearized mappings (thousands, or hundreds, or sometimes just dozens of years from the present time) should be considered approximate, pending additional analysis, especially in these cases:

• A) objects with numerous close planetary encounters (dozens),
• B) objects with very close planetary encounters (< 0.01 AU),
• C) objects with very short data arcs (days or weeks).

While linearized projections will tend to indicate such cases with obviously rapid uncertainty growth, the specific numbers output can tend to understate orbit uncertainty knowledge. Saros136 (talk) 10:10, 22 November 2011 (UTC)

Another explaination:

Output for asteroids and comets can include formal +/- 3-standard-deviation statistical orbit uncertainty quantities. There is a 99.7% chance the actual value is within given bounds. These statistical calculations assume observational data errors are random. If there are systematic biases (such as timing, reduction or star-catalog errors), results can be optimistic. Because the epoch covariance is mapped using linearized variational partial derivatives, results can also be optimistic for times far from the solution epoch, particularly for objects having close planetary encounters

Saros136 (talk) 17:29, 24 November 2011 (UTC)

I still see no reason to remove JPL's projected (best-fit) "uncertainty region" for the 2127 passage. JPL's best-fit solution may not include the Yarkovsky effect that can also cause minor perturbations. I also think it is best to explain (in the article) why JPL does not list results after the close-approach of 2127. -- Kheider (talk) 19:08, 24 November 2011 (UTC)

JPL's calculation does indeed belong. But is not the lack of any non-gravitational perturbations that means we cannot take the min/max distances as absolute boundaries. As far as I can tell the model only gravitational factors, and the uncertainties involved are just measurement and computational ones. They just choose to use a range corresponding to a confidence level, like the error margins given with polls, or circular error probables given by GPS units. I was only objecting to presenting it as absolute limits. Saros136 (talk) 19:59, 24 November 2011 (UTC)

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