Near Earth object
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). NEOs include near-Earth asteroids (NEAs) and near-Earth comets.
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 exploded over the basin of the Podkamennaya Tunguska River. It released an energy of 10–15 megatons of TNT and destroyed roughly 2,000 square kilometres of forest. Such an explosion could have razed London about as far out as the M25 ring road. 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.
References[change | change source]
- "NEO Groups". NASA. http://neo.jpl.nasa.gov/neo/groups.html. Retrieved 2014-09-03.
- "Asteroid Threats: A Call for Global Response". Association of Space Explorers. 2008. http://space-explorers.org/ATACGR.pdf. Retrieved 2014-09-03.
- 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
- 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