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10/24/2003 Archived Entry: "Potentially Hazardous Asteroids"

Potentially Hazardous Asteroids link ... note definitions: "Potentially Hazardous Asteroids (PHAs) are currently defined based on parameters that measure the asteroid's potential to make threatening close approaches to the Earth. Specifically, all asteroids with an Earth Minimum Orbit Intersection Distance (MOID) of 0.05 AU or less and an absolute magnitude (H) of 22.0 or less are considered PHAs. In other words, asteroids that can't get any closer to the Earth (i.e. MOID) than 0.05 AU (roughly 7,480,000 km or 4,650,000 mi) or are smaller than about 150 m (500 ft) in diameter (i.e. H = 22.0 with assumed albedo of 13%) are not considered PHAs. " The J2000 heliocentric ecliptic orbital elements for 540 PHAs is located here. Units to remember: Astronomical distance Unit: 1.0 AU is about 1.5x10^8 km (roughly the average distance between the Earth and the Sun); Lunar Distance: 1 LD = 384,401 km, the distance between Earth and the Moon. 1 LD also equals 0.00256 AU.