Possible Earth impact in 2030 by asteroid 2000 SG344 No Longer a Concern

NEO UPDATE: According to the IAU: "On the afternoon of November 3, Carl Hergenrother of the Catalina Sky Survey (CSS) near Tucson, Arizona, obtained and made available additional observations of object 2000 SG344 from the CSS image archives. These pre-discovery observations significantly improved the certainty of the object's position in 2030 and effectively ruled out the chance of an Earth impact in that year."

° Additional Information on Asteroid 2000 SG344, IAU

° New Results for Object 2000 SG344, NASA JPL

Earlier Information from the NASA ARC NEO Newsletter

NEO News (11/3/00) Possible impact prediction

Dear Friends and Students of NEOs:

Information is being released this morning from NASA and the International Astronomical Union (IAU) concerning a possible impact in 2030 by asteroid 2000 SG344. This is the first verified impact prediction at a level of probability (1 in 500) to put it above hazard level 0 on the Torino hazard scale. While this prediction is no cause for alarm, it certainly focuses attention on the long-term impact hazard. Since the asteroid has a very small space velocity with respect to the Earth, it would be rather likely to survive down to the surface in the unlikely event of an impact in 2030. The energy is such a case would be about 1/10 of the Tunguska impact and about 100 times the Hiroshima bomb. Additional observations this winter may significantly improve the orbit, but unfortunately it already seems to be out of the range of even the powerful Arecibo radar. Definitive information on the orbit might therefore not be obtained until 2028, as it again approaches the Earth.

David Morrison

Following is a statement prepared by Don Yeomans of JPL:

Recent computations by a group of international experts suggest a very small asteroid-like object, designated 2000 SG344, has a remote 1 in 500 chance of impacting the Earth in 2030. These results have been verified by a Technical Review Team of the International Astronomical Union. The greatest likelihood is that future observations of the object will yield higher precision orbit computations that will show with certainty that it will miss the Earth entirely. The unusual nature of the orbit of 2000 SG344 suggests the possibility that it is simply a man-made rocket booster from the Apollo era.

Object 2000 SG344 was discovered on September 29, 2000 by David J. Tholen and Robert J. Whiteley using the Canada-France-Hawaii 3.6-meter aperture telescope on the island of Hawaii. Shortly thereafter, pre-discovery observations taken in May 1999 by MIT's LINEAR observatory team were also identified. Given the observed brightness of the object and its assumed reflectivity, an estimate can be made for its diameter. While the reflectivity of this object is not known, values typical for near-Earth asteroids imply this object's extent is about 30-70 meters. Paul Chodas of the Near-Earth Object Program Office at NASA's Jet Propulsion Laboratory estimates a one in 500 chance of it hitting the Earth on September 21, 2030. The possibility of an Earth impacting orbit was confirmed by Steven Chesley (NASA/JPL), Giovanni Valsecchi (Italian National Research Center in Rome Italy), Andrea Milani (University of Pisa, Italy) and Karri Muinonen (University of Helsinki). If the object is near the large end of the estimated size range for an asteroid, it would be classified as category 1 within the 10 point Torino Scale,meaning the object is one that merits careful monitoring. If the object's size is closer to the lower limit of 30 meters, it would be classified as Torino Scale 0 and hence not of immediate concern.

Because the orbital period of this object about the sun is 354 days, it moves a bit faster than the Earth about the Sun so it is drifting slowly away and will not return to the Earth's neighborhood until nearly three decades. It was last in the Earth's neighborhood in 1971. As yet undiscovered pre-discovery observations made in 1971 and additional observations made in the coming months would provide the data for further refining this object's orbit and the circumstances of its close Earth approach in 2030. During the 2030 close approach, the perturbative effects of the Earth upon the object could change its orbital period so that numerous encounters might be possible after 2030. The likelihood of this situation is also under study.

Because of its Earth-like orbit, this object is an obvious candidate for being a left-over space probe or rocket stage. For example, the S-IVB stages of the five Apollo rockets (Apollo 8-12) entered into heliocentric orbits that are similar to the orbit of object 2000 SG344. If this objectis a man-made rocket booster, it would have a higher reflectivity than a natural asteroid and hence it would have to be smaller (about 15 meters)to reflect as much light as a much darker asteroid. While object 2000SG344 seems too bright to be an Apollo rocket booster, the possibility of its being man-made has not been ruled out.

While object 2000 SG344 will likely pass close to the Earth in 2030, it should be made clear that the probability of the object missing the Earth is at least 500 to 1. If the ongoing studies determine that this object is likely to be a relatively small man-made booster then such a lightweight object would pose no hazard. It is interesting to note the chance of object 2000 SG344 striking the Earth in 2030 is actually less than the chance of an undiscovered object of the same size striking the Earth in any given year. Thus object 2000 SG344 is more interesting than threatening but the international efforts to characterize the nature and future motion of this object will continue.

Added note: The International Astronomical Union (IAU)was closely involved in the verification of the orbit predictions. The IAU has noted that this is the first time the new IAU procedures for technical review have resulted in the verification of a significant impact risk (Torino scale hazard index 1). The IAU system worked very well an stands as an example of international collaboration. The IAU statement concerning the technical review of the orbital calculations is posted on the IAU webpage (http://www.iau.org/sg344.html).

Web page addresses for:

  • Torino Scale: http://impact.arc.nasa.gov/torino/index.html

  • NASA Near-Earth Object web site at JPL: http://neo.jpl.nasa.gov

  • NEODyS web site at University of Pisa: http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?objects:2000SG344;main

  • NASA/Ames NEO Impact Hazard page: http://impact.arc.nasa.gov


  • NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory
    Steve Chesley
    Paul Chodas
    Don Yeomans, Manager

  • Chair, International Astronomical Union Working Group for Near-Earth Objects
    David Morrison, NASA/Ames

  • University of Pisa, Italy
    Andrea Milani

  • University of Helsinki
    Karri Muinonen

  • Italian Space Research Center
    Giovanni Valsecchi

  • Torino Scale
    Richard Binzel, MIT

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