Asteroids which have an orbit that crosses the orbit of the Earth and have a period longer than 1 year. They have a semimajor axes greater than 1 astronomical unit (au), and perihelion distances less than 1.017 au.

An asteroid whose orbit brings it closer than 1 astronomical unit to the sun.

Asteroid having orbital parameters similar to the Earth's.

an asteroid whose orbit crosses the Earth's orbit

See Earth-crossing asteroid.

minor planet whose orbit passes within that of Earth, but whose average distance from the Sun is greater than 1.0. astronomical unit.

The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, the first asteroid of this group to be discovered by Karl Wilhelm Reinmuth. They are Earth-crosser asteroids that have orbital semi-major axes greater than that of the Earth. Some can get very close to the Earth, making them a potential threat to our planet (the closer their semi-major axis is to Earth's, the less eccentricity is needed for the orbits to cross).