An artist's impression of a protoplanetary disc, which surrounds a newly formed star and which ultimately turns into planets.
Credit: Wikipedia
BRISBANE: The Solar System must be about two million years older than previously thought, scientists discovered when they looked at the oldest meteorite.
The revised older age comes from an analysis of relict minerals contained within a meteorite — called calcium-aluminium-rich inclusions (CAIs) — found in northwest Africa.
"These mineral inclusions were the first large objects formed in the Solar System" says cosmochemist Audrey Bouvier from Arizona State University and lead author of the study published in Nature Geoscience, "and as such they are considered the oldest objects in the Solar System."
Two million years older
All material contains naturally occurring radioactive isotopes that decay into other elements, and by determining the relative abundance of the isotopes and their decay products, the age of a sample can be determined. This process is known as radioactive dating.
For samples of this age, the most common method is to compare the levels of two different uranium isotopes, which decay into two different lead isotopes.
With incredible precision, the research team was able to measure the quantities of these isotopes in the inclusions, and used the ratios of these isotopes to infer the age of the inclusion.
Oldest materials from the Solar System
The findings show that the inclusion was formed 4,568.2 million years ago — between 0.3 and 1.9 million years earlier than previous estimates, making it the oldest material from the Solar System that has been dated so far.
Not only were the researchers able to revise the age of the Solar System, but they were also able to make profound insights into what was happening during the early years of the Solar System.
It is generally accepted that the Solar System commenced life as a protoplanetary disc - a large gaseous cloud that condensed into small solid grains (CAIs), however, this study now details exactly how this occurred, and over what time-frame the events happened.
"By doing high precision measurements we shed light on processes that happened, and that we were previously not aware of" says Bouvier.
The study shows that the Solar System evolved in its early days by condensing the gaseous clouds into small particles. However, relatively soon afterwards (~ two million years) it appears as though material was injected into the Solar System from nearby supernovae (dying stars).
