Earth-crossing Asteroid on:
[Wikipedia]
[Google]
[Amazon]
An Earth-crosser is a
retrieved online
May 3, 2009. Of the Earth-crossing asteroids, 3753 Cruithne is notable for having an orbit that has the same period as Earth's.
Very Close Approaches (<0.01 AU) of PHAs to Earth 1900–2200
Upcoming Close Approaches (<0.10 AU) of Near-Earth Objects to Earth
-Sormano Astronomical Observatory
-Sormano Astronomical Observatory
-Sormano Astronomical Observatory
-Minor Planet Center {{DEFAULTSORT:List Of Earth-Crossing Minor Planets * Earth-crossing Earth-crossing Planetary defense
An Earth-crosser is a near-Earth asteroid
A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun (perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit aro ...
whose orbit
In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...
crosses that of Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
as observed from the ecliptic pole of Earth's orbit. The known numbered Earth-crossers are listed here. Those Earth-crossers whose semi-major axes are smaller than Earth's are Aten asteroids; the remaining ones are Apollo asteroids. ''(See also the Amor asteroids.)''
An asteroid with an Earth-crossing orbit is not necessarily in danger of colliding with Earth. The orbit of an Earth-crossing asteroid may not even intersect with that of Earth. This apparent contradiction arises because many asteroids have highly inclined orbits, so although they may have a perihelion
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values.
Apsides perta ...
less than that of Earth, their paths can never cross. An asteroid for which there is some possibility of a collision with Earth at a future date and which is above a certain size is classified as a potentially hazardous asteroid (PHA). Specifically, an asteroid is a PHA if its Earth minimum orbital intersection distance (MOID) is <0.05 AU and its absolute magnitude is 22 or brighter. The concept of PHA is intended to replace the now abandoned strict definition of ECA (Earth-crossing asteroid) which existed for a few years. Determining if an asteroid was an ECA required calculation of its orbits millennia into the future, including planetary gravitational perturbations, to assess whether a collision with Earth was possible and this has proved to be impractical.
Having a small MOID is not a guarantee of a collision. On the other hand, small gravitational perturbations of the asteroid around its orbit from planets that it passes can significantly alter its path. For instance, 99942 Apophis will approach Earth so closely in 2029 that it will get under the orbit of the Earth's geostationary satellites.Dr. Tony Phillips, "Friday the 13th, 2029", ''Science@NASA''retrieved online
May 3, 2009. Of the Earth-crossing asteroids, 3753 Cruithne is notable for having an orbit that has the same period as Earth's.
List
''Notes:'' † outer-grazerSee also
*Earth-grazing fireball
An Earth-grazing fireball (or Earth grazer) is a fireball (meteor), fireball, a very bright meteor that enters Earth’s atmosphere and leaves again. Some fragments may impact Earth as meteorites, if the meteor starts to break up or explodes in m ...
* List of asteroid close approaches to Earth
* Asteroid impact avoidance
Asteroid impact avoidance encompasses the methods by which near-Earth objects (NEO) on a potential collision course with Earth could be diverted, preventing destructive impact events. An impact by a sufficiently large asteroid or other NEOs w ...
* List of Mercury-crossing minor planets
A Mercury crosser or Mercury grazer is an asteroid whose orbit crosses that of Mercury. The Mercury crossers proper have aphelia outside Mercury's (0.4667 AU) and perihelia inside Mercury's (0.3075 AU), whereas those listed here as outer grazer ...
* List of Venus-crossing minor planets
* List of Mars-crossing minor planets
* List of Jupiter-crossing minor planets
* List of Saturn-crossing minor planets
* List of Uranus-crossing minor planets
* List of Neptune-crossing minor planets
References
External links
Very Close Approaches (<0.01 AU) of PHAs to Earth 1900–2200
Upcoming Close Approaches (<0.10 AU) of Near-Earth Objects to Earth
-Sormano Astronomical Observatory
-Sormano Astronomical Observatory
-Sormano Astronomical Observatory
-Minor Planet Center {{DEFAULTSORT:List Of Earth-Crossing Minor Planets * Earth-crossing Earth-crossing Planetary defense