Abstract
About 4700 potentially hazardous asteroids (PHAs) come within 8 million kilometers of Earth and are big enough to cause regional or larger‐scale damage, according to results from NEOWISE, the near‐Earth‐object observing component of NASA's Wide‐field Infrared Survey Explorer (WISE), which NASA released on 16 May. The total number of PHAs with diameters larger than about 100 meters could be 1500 more or less than the total announced, and about 20%–30% of those asteroids have been found, according to NASA. The number of PHAs is similar to predicted numbers from earlier estimates, but because the WISE telescope detected infrared light from asteroids, the new study provides a more credible estimate of the number and sizes of PHAs, according to NASA. In addition, the results suggest that about twice as many PHAs as previously thought may reside in lower‐inclination orbits more aligned with the plane of the Earth's orbit. Those asteroids are more likely to come close to the Earth, and they may also be easier to explore.
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