Near Earth object

From Wikipedia, the free encyclopedia
Jump to: navigation, search

A near Earth object (NEO) is a Solar System object whose orbit brings it close to the Earth. The perihelion of all NEOs, their least distance to the Sun, is less than 1.3 AU (194,000,000 km).[1] NEOs include near-Earth asteroids (NEAs) and near-Earth comets.[1]

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 bolide of around 45 metres in diameter[2] exploded over the basin of the Podkamennaya Tunguska River.[3] It released an energy of 10–15 megatons of TNT[3] and destroyed roughly 2,000 square kilometres of forest.[4] Such an explosion could have razed London about as far out as the M25 ring road.[4] 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.[2]

References[change | change source]

  1. 1.0 1.1 "NEO Groups". NASA. http://neo.jpl.nasa.gov/neo/groups.html. Retrieved 2014-09-03.
  2. 2.0 2.1 "Asteroid Threats: A Call for Global Response". Association of Space Explorers. 2008. http://space-explorers.org/ATACGR.pdf. Retrieved 2014-09-03.
  3. 3.0 3.1 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
  4. 4.0 4.1 Napier, Bill; Asher, David (2009), "The Tunguska impact event and beyond", Astronomy & Geophysics 50 (1): 1.18–1.26, doi:10.1111/j.1468-4004.2009.50118.x