Asteroids are potentially make dangerous to the earth

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Near Earth Object (ODB) is a variety of asteroids whose orbits are close to Earth. This Gaspra asteroid image was taken through the Galileo spacecraft. Although not in the ODB category, the Gaspra surface resembles some ODB. ODB is also most likely the aim of astronauts. The SAO astronomers announced the first results of the largest program now underway to determine the size and characteristics of ODB. Photo Courtesy NASA.

Even a 1-km ODB impact could destroy an average of one province. The 1908 Tunguska event that flattens over 2000 square kilometers in Russia is thought to be caused by an asteroid having a diameter of only about 60 meters. Therefore representatives of the US people mandate within 10 years to make a list of 90% total ODB diameter greater than 140 meters.

It is generally easy to detect an ODB in visible light by observing its movement across the sky from night to night. However, getting the size is more difficult. The problem is that ODB optical light is the result of both size and albedo / reflectivity, and it is impossible to determine an asteroid size only from optical light alone. So far, only about 1.5% of ODB has been measured, and many of them are generally large. Astronomers predict that there is more than a tenfold ODB diameter measuring 100 meters from a diameter of 1 km, because the scale of the rough approximate damage such as the asteroid volume, the size of 100 meters less than 1000 times the damage.

CfA Joe Hora astronomers Giovanni Fazio, Howard Smith and Tim Spahr formed a team of six astronomers to study ODB on the size of infrared waves in which ODB emits its own radiation as well as reflects sunlight. The infrared light when combined with the optical value allows scientists to draw conclusions about size and reflectivity or albedo. Moreover, since albedo is part of the asteroid surface characteristics and mineralogical composition, the results help to determine the nature of the asteroid, and from that it may be known where it came from in the solar system, and how it developed.

The results represent a dramatic contribution to the challenges given by US representatives to create potentially harmful ODB lists, and increase our understanding of the physical processes that have shaped the solar system since it formed 5 billion years ago.

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