Often scientists talk about the cosmic timescale. For humans, a decade is often viewed as a long time. On a cosmic timescale, 10 years or even a hundred years is the blink of an eye. Cosmic timescales are measured in millions or billions of years. Scientists from the Lawrence Livermore National Laboratory recently announced that research indicates our solar system formed in less than 200,000 years.
On a cosmic scale, that is very fast. Researchers came to this conclusion after looking at isotopes of the element molybdenum found in meteorites. The material makes up the sun and the rest of the solar system and came from the collapse of a large gas and dust cloud about 4.5 billion years ago. By observing other solar systems that formed similarly to our solar system, astronomers were able to estimate that it likely took about 1 to 2 million years for the collapse of the cloud and the ignition of a star.
Before this study, the solar system formation timeframe was not clearly known. The new research shows the gaseous cloud collapse that led to the formation of the solar system happened very quickly, in less than 200,000 years. To put this timeframe in a better perspective, scientists on the project say that if we scale this to compare to human pregnancy, the pregnancy would last about 12 hours rather than nine months.
The oldest dated solids in the solar system are calcium-aluminum-rich inclusions (CAIs). The samples provide a direct record of the formation of our solar system. CAIs are micrometer two centimeter-sized inclusions and meteorites that formed in high temperatures of over 1300 degrees Kelvin, likely near the young sun.
The CAIs were then transported outward to a region where carbonaceous chondrite meteorites formed. The majority of CAIs formed 4.567 billion years ago, over about 40,000 to 200,000 years. By measuring the molybdenum isotopic and trace element compositions of various CAIs from carbonaceous chondrite meteorites, the team found the distinct isotopic compositions of CAIs cover the entire range of material that formed in the protoplanetary disc instead of a small slice. That means the inclusions must’ve formed within the time span of cloud collapse.