The Murchison meteorite fell to Earth in 1969 Credits: JAMES ST JOHN

OLDEST STAR-DUST DISCOVERED ON EARTH IN 2020

The grains of dust are even older than our own sun’s formation trapped inside the meteor piece.

Rocking researchers at the University of Chicago and Field Museum USA found the most ancient solid material within the reach of humanity, it’s age is around 7,000,000,000 years.

The grains of dust are even older than our own sun’s formation trapped inside the meteor piece. There the grains remain for billions of years and such meteorite was found in Australia. These grains also offer us clues about the massive star formation campaign at that time. 

The study was published in a paper on Jan 13, 2020 Proceedings of National Academy of Sciences, the author Philipp Heck says “This is one of the most exciting studies I’ve worked on, These are the oldest solid materials ever found on the planet, and they tell us how stars formed in our galaxy.”

We usually see stars as fixed stable objects in the sky. But, astrophysically we know they have life cycles, from birth to death. Dust and gaseous clouds form stars in interstellar nurseries, forged by the reckoning force of gravity. Then, they burn for millions to billions of decades, and then they die. At the perfect moment of their death, their particles spread into space, in form of new stars, planets.— also in meteorites.  

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Scientists took electron microscope photos to be able to see the grains—this one is eight microns across, about the size of a single red blood cell. Credits: Janaína N. Ávila

Within meteorites, it is a daunting a task to discover presolar grains, they are extremely rare, only found 5% of the time. Now, at the Field Museum, we have the largest part of the Murchison meteorite, a true nature’s masterpiece with presolar grains that were fallen around 50 years ago, and was made available to science by the people of Murchison, Victoria. 

Jennika Greer, a graduate student at the University of Chicago and co-author of the study says, “It starts with crushing fragments of the meteorite down into a powder.”, Once all the pieces are segregated, a kind of paste, and it has a pungent characteristic, it smells like a rotten peanut butter. For the analogy, this Rotten-peanut-butter-meteorite-paste is mixed with acid until only the presolar grains remained present. Once the presolar were isolated, the researched used a rigorous process based on cosmic rays to figure out from what types of stars they came and how old they were.

“We used exposure data, which measures the exposure of grains to the cosmic rays, as cosmic rays are high energy particles that fly through our galaxy and penetrate with the solid matter”, said Heck. She works in pioneering new scientific methods to understand Astrophysics’ phenomenal questions by investigating meteorites. 

Some of the pre-solar grains in the Murchison meteorite (inset) could have come from evolved stars similar to the Egg Nebula (pictured) Credits: ESA/HUBBLE/NASA/JANAÍNA ÁVILA
Some of the pre-solar grains in the Murchison meteorite (inset) could have come from evolved stars similar to the Egg Nebula (pictured) Credits: ESA/HUBBLE/NASA/JANAÍNA ÁVILA

To find out their age, we need to know how many elements were produced by the cosmic rays within the presolar grains.“Some of these cosmic rays interact with the matter and form new elements. And the longevity of exposure equals to more those elements”.

The meteor scientists found out that the presolar grains in the sample were the oldest ever discovered. Due to the high amount of cosmic radiation they soaked up in, most of them had the age of 4.6 to 4.9 billion years old, and some other grains were even older than 5.5 billion years — In order, to grab the understanding and relevancy here, the age of the sun is 4.6 billion years old, and the planet Earth is 4.5 billion. 

The story doesn’t end here, as the presolar grains formed when a star dies. They are also valuable to tell us about the ancient history of the stars. Yet, we hypothesize that 7 billion years ago, there would have been a loud boom in star formation. 

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Dr Philipp R. Heck is an Associate Professor University of Chicago’s Department of the Geophysical Sciences and Curator of Meteoritics and Polar Studies at the Field Museum of Natural History in Chicago. Image Credits: Australian Institute of Geoscientists

This rocking evidence is now a debate between scientists about whether new stars form at a steady rate or if there are high and lows in their number over time. “Some of the people in the science community think that the star formation rate within a galaxy is constant.”, “But thanks to these grains, we now have direct evidence for a period of enhanced star formation in our galaxy seven billion years ago with samples from meteorites. This is one of the key findings of our study,” said Heck.

Associate Prof. Philipp Heck: “This is one of the most exciting studies I’ve worked on. These are the oldest solid materials ever found, and they tell us about how stars formed in our galaxy.”

Other study co-authors came from Lawrence Livermore National Laboratory, Washington University, Harvard Medical School, ETH Zurich, and the Australian National University. 

Citation: “Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide.” Proceedings of the National Academy of Sciences. Jan 13, 2020.

Reference: https://www.pnas.org/content/117/4/1884

Read, Also; A New Phenomenon of Origination of Planets & Stars as “Twins”

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