| |
| | Near-Earth Asteroids |
 | | Apollo asteroids have semimajor axes (a) that are greater than or equal to 1 AU and perihelion distances that are less than or equal to 1.0 AU; thus, they cross the Earth's orbit when near the perihelia of their orbits. |
 | | By mid-1991 the number of known Aten, Apollo, and Amor asteroids were 11, 91, and 81, respectively. |
 | | Most of these were discovered since 1970, when dedicated searches for this type of asteroid were begun: 25 were discovered during the 1970s, 80 during the 1980s, and 49 during the first 20 months of the 1990s. |
| abyss.uoregon.edu /~js/glossary/near_earth_asteroids.html (336 words) |
|