It was reported today that an Asteroid 31 miles wide and around 47 meters across aptly named ‘2009 DD45′, flew past the earth at 13:44 UK time this Monday the 3rd March 2009, reports the Planetary Society and astronomers’ blog. The closeness to an earth impact was mere 72,000 kilometres, or a one-fifth of the distance between Earth and the Moon and just twice the height of communication satellites in geosynchronous orbit, stated the website space.com.
The approximated size is equivalent to that of the asteroid that impacted above Tunguska, Siberia, on June 30th 1908, crushing 80 million trees in an area of more than 2,000 square kilometres. ‘2009 DD45’ was sighted last Saturday by astronomers at the Siding Spring Survey in Australia, and was confirmed by the International Astronomical Union’s Minor Planet Centre, which records Solar System rocks.
Asteroids are material left over from the establishment of the solar system. They are also known as ‘planetesimals which originated from the birth of our solar system and have altered very little since the breakdown of the solar nebula 4. Asteroids are segmented into three chief categories depending on their chemical structure and their reflective strength with C-type asteroids creating around 75% of them.
Asteroids usually absorb more sunlight than they reflect and are concentrated in the asteroid belt because of orbital resonances between asteroids and Jupiter. These unusual orbits are the consequence of Jupiter’s gravity, pulling the asteroid out of its primary orbit into a new one.
Most asteroids are known to be located within the asteroid belt which is positioned between the orbit of Jupiter and Mars. Alternatives, are more distant objects, with highly changeable orbits, such as the Trojans, which reside within the orbit of Jupiter, or the Centaurs, which are located in our very outer solar system. Many missions have been launched from Earth to explore these rocky fragments and NASA’s Galileo mission piloted past two principal belt asteroids, Ida and Gaspra, in the early 1990s on route to Jupiter. In the year 2000, the NEAR Shoemaker satellite steered past asteroid Mathilde in advance of orbiting near Earth asteroid Eros.
These nearby asteroids are named Potentially Hazardous Asteroids or PHAs since they could impact with the Earth as colossal meteorites. The extermination of the dinosaurs 65 million years ago has been associated to a destructive impact near the Yucatan peninsula in Mexico.
The makeup of an asteroid is thought to be related to the Sun, drained of hydrogen, helium, and other volatiles. Composition of studies samples conclude the materials which formed these objects to be primarily metallic iron mixed with iron and magnesium silicates. There are primarily 4 kinds of asteroids which fall into one of either composition groups including; ‘S’ type (silicon rich), ‘M’ type (nickel iron rich), ‘C’ type (carbon rich) and objects made up from natural organic materials named the ‘D’ type. Many asteroids and meteorites almost certainly have related compositions, so asteroids may be the mother bodies of meteorites.
Only a handful asteroids are of any magnitude, with only one of the 600 miles diameter and three further objects known to exist at around 300 miles in diameter meaning that today’s report of an Asteroid 31 miles wide is considered to be somewhat of a baby sized space rock.