Hernan Canellas/MIT
Astronomers have estimated the new lifetime of the solar nebula which suggests
that the gas giant planets Jupiter and Saturn formed within the first four
million years of our solar system's formation.
About 4.6 billion years ago, an
enormous cloud of hydrogen gas and dust collapsed under its own weight,
eventually flattening into a disk called the solar nebula.
Most of this interstellar material
contracted at the disk's centre to form the Sun, and part of the solar nebula's
remaining gas and dust condensed to form the planets and the rest of our solar
system.
Now, scientists from Massachusetts
Institute of Technology (MIT) in the US and their colleagues have estimated the
lifetime of the solar nebula - a key stage during which much of the solar
system evolution took shape.
This new estimate suggests that the
gas giants Jupiter and Saturn must have formed within the first four million
years of the solar system's formation.
Furthermore, they must have
completed gas-driven migration of their orbital positions by this time.
Benjamin Weiss, a professor at MIT and Huapei Wang, the first author of the
research, studied the magnetic orientations in pristine samples of ancient
meteorites that formed 4.653 billion years ago, determining that the solar nebula
lasted around three to four million years.
This is a more precise figure than
previous estimates, which placed the solar nebula's lifetime at somewhere
between one and 10 million years.
The team came to its conclusion
after carefully analysing angrites, which are some of the oldest and most
pristine of planetary rocks. Scientists view angrites as exceptional recorders
of the early solar system, particularly as the rocks also contain high amounts
of uranium, which they can use to precisely determine their age.
Now that the scientists have a
better idea of how long the solar nebula persisted, they can also narrow in on
how giant planets such as Jupiter and Saturn formed.
Source: DNA-14th February,2017
