One such Earth-crossing asteroid is Toutatis, which was discussed in the preceding section.
Earth-crossing asteroid An asteroid whose orbit crosses that of the Earth. Earth-crossing asteroids are also called Apollo asteroids, after the first of the type discovered.
Earth-crossing asteroids pose a very real (if statistically unlikely) danger to the . An impacting asteroid makes a crate about 10-20 times its size.
An Earth-crossing asteroid (No. 1685) discovered by Wirtanen in 1948 and rediscovered in 1964, of irregular shape (about 5 x 3 km), whose closest approach takes it within 0.13 AU of Earth. Perihelion distance 0.77 AU; aphelion distance 1.96 AU; e = 0.
Although they are thought to account for only about 5-10% of the impacts, they approach Earth with greater speeds and higher energies than Earth-crossing asteroids of the same size (the nucleus of a comet, ...
Earth-Crossing Asteroids
Although by definition no Amor asteroid actually currently crosses the Earth's orbit (see Earth-crosser asteroid), the definition of an Earth-crossing asteroid (ECA) is broad enough so that many, if not most, ...
In the course of our search for Earth-crossing asteroids, we could find one that will hit not in the next year, or even in the next ten years, but might hit in the next hundred years.
All the meteorites mentioned above come from the Main Asteroid Belt that occupies the space between Mars and Jupiter, and from Earth-crossing asteroids whose orbits extend inside Earth's orbit.
Geographos is classified as an Earth-crossing asteroid because its orbit can evolve to intersect Earth's orbit. Scientists have found fewer than 300 Earth-crossing asteroids; however, they believe hundreds of thousands of objects might exist.
Aten -- A class of Earth-crossing asteroid.
Attometer -- 10-18 meter.
Astronomical Twilight -- For technical definition, please follow this link to the U.S. Naval Observatory Astronomical Applications website.
Earth-crossing asteroids may collide with Earth, a worrisome possibility.
Also known as Earth-crossing asteroids, one of three groups of near-Earth asteroids. Apollo group asteroids have semimajor axes greater than 1.0 AU and perihelia less than 1.017 AU (Earth's aphelion distance).
It is theorized that some of the Earth-crossing asteroids and the great majority of meteorites reaching Earth’s surface are fragments produced in collisions similar to those that produced the asteroid families.
criterion of the definition makes a lot of people scratch their heads. Could the Earth clear the Kupier Belt if it were moved there? Has it even cleared its own orbit of pesky things like the Moon, not to mention hundreds of Earth-crossing asteroids?
For the other group of Earth-crossing asteroids -- named Atens after 2062 Aten, which was discovered in 1976 by Eleanor F. Helin of the United States, D 0.983 AU, the present perihelion distance of the Earth.
In most cases, however, the effect is small enough that even after billions of years most satellites will not actually be lost. The effect is probably most pronounced for Mars' second moon Deimos, which may become an Earth-crossing asteroid after it ...
 See also: Earth, Asteroid, Asteroids, Orbit, Time
  
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