The processes that created our Solar System are quite well understood. About 4.56 billion years ago, plumes of gas ejected by a local supernova (as well as ejecta from other stars, and interstellar materials) started collapsing under its own gravitational force. The central region of the collapsing gas grew larger, and slowly an accretion disk formed around it. After a few million years, the central region got so dense that nuclear fusion started at its core: we had the birth of our Sun. The accretion disk slowly coalesced into the planets and asteroids, and the left over material formed comets and meteors. Now for the first time, scientists have precisely dated the age of this seminal event, and how long it took the gases to coalesce into the Sun and planets.

Allende Meteorite (Courtesy: LLNL)Chondrules are small silicate spheres in many meteorites, and represent the oldest solid material within our solar system and are believed to be the building blocks of the planetary system. Another common component of meteorites are the Calcium Aluminium-rich inclusions (CAIs). By looking at the content of these two in the primitive meteorite Allende (fell on Mexico in 1869), Lawrence Livermore Lab physicist Ian Hutcheon, with colleagues from the University of Hawaii at Manoa, the Tokyo Institute of Technology and the Smithsonian Institution, found that the age difference between them points directly to the lifetime of the solar nebula.
The researchers found that CAIs were formed in an oxygen-rich environment and date to 4.567 billion years old, while chondrules were formed in an oxygen setting much like that on Earth and date to 4.565 billion, or less, years old. Therefore, it took about 2 million years for the solar nebula to coalesce, and form the Sun and planets, including Earth :):). Also, the age of the Earth is therefore quite precisely fixed at between 4.565 and 4.567 billion years! :D.