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UH Observations Result in “All Clear” for Potential Asteroid Impact
University of Hawaii at Manoa astronomers made new observations of asteroid 2011 AG5 that show that this asteroid, previously thought to have a significant potential to threaten Earth, no longer poses a significant risk of impact, NASA announced today. The orbital uncertainties of the 140-meter-diameter near-Earth asteroid had previously allowed a 0.2 percent chance of collision in February 2040, leading to a call for more observations to better constrain the asteroid’s future course.
Answering the call, David Tholen, Richard Wainscoat and Marco Micheli of the UH Institute for Astronomy used the 8-meter Gemini North telescope on Mauna Kea, Hawaii, to find the small, very faint asteroid on October 20, 21 and 27, 2012.
An analysis of the new data conducted by NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California, shows that the risk of collision in 2040 has been eliminated. The updated trajectory of 2011 AG5 is not significantly different, but the new observations have reduced the orbit uncertainties by more than a factor of 60, meaning that Earth’s position in February 2040 no longer falls within the range of possible future paths for the asteroid. With the updated orbit, the asteroid will pass no closer than 890,000 km (550,000 miles, over twice the distance to the moon) in February 2040, the time of the prior potential collision.
This result was expected. Earlier in 2012, NASA’s NEO Program Office conducted a contingency deflection analysis for the 2040 potential impact of 2011 AG5. Among the findings was that any new observations either in 2012 or in 2013, when the object will be much easier to observe, had a 95 percent likelihood of eliminating the hazard posed by 2011 AG5. If the potential for impact had been confirmed the impact odds could have risen as high as 1 in 10, but the May 2012 study found that scenario to be unlikely. While the interest in 2011 AG5 has been reduced by the new results, the experience gained by studying this real-world deflection problem has demonstrated that NASA is well situated to detect and predict the trajectories of Earth-threatening asteroids.
In addition to the Gemini measurements, Tholen, Micheli, and Garrett Elliott obtained less conclusive observations in September and earlier in October with the UH 2.2-meter telescope, also on the summit of Mauna Kea. Tholen explained, “As it turns out, the asteroid is highly variable in brightness, which is probably why we were unable to make definitive observations on the smaller telescope.”
The data are being published by the Minor Planet Center in Cambridge, Mass.
Quelle:University of Hawaii
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"All Clear" Given on Potential 2040 Impact of Asteroid 2011 AG5
NASA/JPL Near-Earth Object Program Office
December 21, 2012
NASA scientists have announced that new observations of 2011 AG5 show that this asteroid, once thought to have a worrisome potential to threaten Earth, no longer poses a significant risk of impact. The orbital uncertainties of the 140m diameter near-Earth asteroid had previously allowed a 0.2% chance of collision in Feb. 2040, leading to a call for more observations to better constrain the asteroid's future course.
Answering the call, University of Hawaii astronomers Dave Tholen, Richard Wainscoat and Marco Micheli used the Gemini 8-meter telescope at Mauna Kea, Hawaii to successfully recover and observe the small and very faint asteroid on October 20, 21 and 27, 2012. In addition to improving our knowledge of the orbit, the Gemini observations also suggest the asteroid varies in brightness as it rotates and therefore may be elongated. Gemini is managed by the Association of Universities for Research in Astronomy (AURA). In addition to the Gemini measurements, Tholen, Micheli and Garrett Elliott obtained less conclusive observations on October 9 & 10 with the University of Hawaii 2.2-meter telescope, also situated on the summit of Mauna Kea. After extensive astrometric analysis by the team in Hawaii, all observations were then sent to the International Astronomical Union's Minor Planet Center in Cambridge, Massachusetts.
An analysis of the new data conducted by NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California, shows that the risk of collision in 2040 has been eliminated. The updated trajectory of 2011 AG5 is not significantly different, but the new observations have reduced the orbit uncertainties by more than a factor of 60, meaning that the Earth's position in February 2040 no longer falls within the range of possible future paths for the asteroid. With the updated orbit, the asteroid will pass no closer than 890,000 km (over twice the distance to the moon) in Feb. 2040, the epoch of the prior potential collision.
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The position data obtained for near-Earth asteroid 2011 AG5 in October 2012 was used to update its orbit and dramatically reduce its future orbital uncertainties in February 2040. In the first plot, the asteroid's possible positions in space (region of uncertainty) prior to the orbit improvement is an extremely lengthy arc that includes the position of the Earth. Hence an Earth collision could not be ruled out. However, the observational data in October 2012 allowed a sixty-fold improvement in the 2040 region of uncertainty and the second plot shows that this, now much smaller, arc no long includes the Earth. Hence an Earth impact by 2011 AG5 in February 2040 is no longer possible.
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Earlier in 2012, NASA's NEO Program Office conducted a contingency deflection analysis for the 2040 potential impact of 2011 AG5. Among the findings was that any new observations either in 2012, or in 2013 when the object will be much easier to observe, had a 95% likelihood of eliminating the hazard posed by 2011 AG5. If the potential for impact had been confirmed, the impact odds could have risen as high as 1 in 10, but the study released in May 2012 found that scenario to be unlikely. While the interest in 2011 AG5 has been reduced by the new results, the experience gained by studying this potential real-world deflection problem has demonstrated that NASA is well situated to predict the trajectories of Earth threatening asteroids.
Quelle: NASA