Near-Earth object

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Flyby of asteroid 2004 FH (centre dot being followed by the sequence). The other object that flashes by is an artificial satellite
Asteroid 4179 Toutatis is a potential hazard that passed within 2.3 lunar distances

A near-Earth object (NEO) is a Solar System object whose orbit brings it close to the Earth.

Their least distance from the Sun, their perihelion, is less than 1.3 AU.[1][2] NEOs include near-Earth asteroids (NEAs) and near-Earth comets.[2]

They include more than ten thousand near-Earth asteroids (NEAs), near-Earth comets, some solar-orbiting spacecraft, and meteoroids large enough to be tracked in space before striking the Earth. Collisions in the past have had a significant role in shaping the geological and biological history of the planet.[3]

In some cases NEOs hit the Earth. Most of these explode harmlessly in the upper atmosphere. But some NEOs are dangerous. On 30 June 1908, a meteorite of around 45 metres in diameter[4] exploded over the basin of the Podkamennaya Tunguska River.[5] It released an energy of 10–15 megatons of TNT[5] and destroyed roughly 2,000 square kilometres of forest.[6] Such an explosion, similar to one of the biggest nuclear weapons, could have razed London about as far out as the M25 ring road.[6] However, because the location was remote, no deaths were recorded. The Association of Space Explorers estimates that a Tunguksa-like event happens two or three times every thousand years on average.[4] An asteroid roughly 10 km in diameter is thought to have hit Earth 66 million years ago and caused the K/T extinction event, including the extinction of all non-avian dinosaurs.[7]

Frequency of small asteroids ~1 to 20 meters in diameter hitting Earth's atmosphere

References[change | change source]

Near-Earth asteroids classification
  1. An astronomical unit (AU) is the semi-major axis of the Earth's orbit. That is the longest distance of the Earth from the Sun.
  2. 2.0 2.1 "NEO Groups". NASA. http://neo.jpl.nasa.gov/neo/groups.html. Retrieved 2014-09-03.
  3. Richard Monastersky (1997). "The call of catastrophes". Science News Online. http://www.sciencenews.org/pages/sn_arc97/75th/rm_essay.htm. Retrieved 2007-10-23.
  4. 4.0 4.1 "Asteroid threats: a call for global response". Association of Space Explorers. 2008. http://space-explorers.org/ATACGR.pdf. Retrieved 2014-09-03.
  5. 5.0 5.1 Farinella P. et al (2001), "Probable asteroidal origin of the Tunguska Cosmic Body", Astronomy & Astrophysics 377 (3): 1081–1097, doi:10.1051/0004-6361:20011054
  6. 6.0 6.1 Napier, B; Asher, D (2009), "The Tunguska impact event and beyond", Astronomy & Geophysics 50 (1): 1.18–1.26, doi:10.1111/j.1468-4004.2009.50118.x
  7. Schulte P. et al (2010), "The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene Boundary", Science 327 (5970): 1214–1218, doi:10.1126/science.1177265