Oldest Material Discovered on Earth: 7 Billion Year Old Stardust
2020-01-20
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1Scientists say they have identified the oldest solid material on Earth - stardust believed to have formed about 7 billion years ago.
2It was found in pieces of meteorite that fell out of the sky in Australia 50 years ago.
3Stardust is matter that forms as small particles in space when stars die.
4These particles can be used later to form new planetary bodies, including stars, planets and moons.
5The meteorite pieces came down in September 1969 in the town of Murchison, in Australia's Victoria state.
6Scientists with the Field Museum of Natural History in the American city of Chicago have long held the largest collection of these pieces.
7But until now, the age of the oldest stardust samples had not been confirmed.
8Researchers at the museum reported their identification last week in Proceedings of the National Academy of Sciences.
9"This is one of the most exciting studies I've worked on," said Philipp Heck, a curator at The Field Museum who led the research.
10"These are the oldest solid materials ever found, and they tell us about how stars formed in our galaxy," he added.
11The scientists said the microscopic particles were made of silicon carbide, the first mineral formed when a star cools.
12All of the samples predate the formation of our own solar system, they noted.
13The researchers said the stardust particles "became trapped in meteorites, where they remained unchanged for billions of years."
14This makes the samples "time capsules" of events that happened before the solar system.
15The identification process first involved crushing the samples down into a fine dust.
16The pieces were then mixed with acid, which left only the pre-solar particles.
17The researchers then examined samples for information that would help them identify what kinds of stars they came from and how old they were.
18In space, dust interacts with cosmic rays -- high-energy particles that move through space at nearly the speed of light.
19Philipp Heck explained that some of these interactions result in the formation of new elements.
20The longer the interactions last, the more elements are formed.
21Age can then be estimated by measuring how many of the new cosmic ray-produced elements were present in pre-solar samples, Heck said.
22Based on examinations of this data, the researchers learned that some of the pre-solar particles were the oldest ever discovered.
23The team identified the age of 40 grains, most of which were estimated to be between 4.6 billion and 4.9 billion years old.
24These ages relate to the time when the first stars began to break up.
25Since that kind of star lived for up to 2.5 billion years, the stardust can be as old as up to seven billion years.
26The latest dating process confirms a scientific theory that predicted "a baby boom of stars" happened before the formation of our sun.
27"We have more young grains than we expected," Heck said.
28He added: "We basically came to the conclusion that there must have been a time in our galaxy when more stars formed than normal, and at the end of their lives they become dust producing."
29I'm Bryan Lynn.
1Scientists say they have identified the oldest solid material on Earth - stardust believed to have formed about 7 billion years ago. It was found in pieces of meteorite that fell out of the sky in Australia 50 years ago. 2Stardust is matter that forms as small particles in space when stars die. These particles can be used later to form new planetary bodies, including stars, planets and moons. 3The meteorite pieces came down in September 1969 in the town of Murchison, in Australia's Victoria state. Scientists with the Field Museum of Natural History in the American city of Chicago have long held the largest collection of these pieces. 4But until now, the age of the oldest stardust samples had not been confirmed. 5Researchers at the museum reported their identification last week in Proceedings of the National Academy of Sciences. 6"This is one of the most exciting studies I've worked on," said Philipp Heck, a curator at The Field Museum who led the research. "These are the oldest solid materials ever found, and they tell us about how stars formed in our galaxy," he added. 7The scientists said the microscopic particles were made of silicon carbide, the first mineral formed when a star cools. All of the samples predate the formation of our own solar system, they noted. 8The researchers said the stardust particles "became trapped in meteorites, where they remained unchanged for billions of years." This makes the samples "time capsules" of events that happened before the solar system. 9The identification process first involved crushing the samples down into a fine dust. The pieces were then mixed with acid, which left only the pre-solar particles. 10The researchers then examined samples for information that would help them identify what kinds of stars they came from and how old they were. 11In space, dust interacts with cosmic rays -- high-energy particles that move through space at nearly the speed of light. 12Philipp Heck explained that some of these interactions result in the formation of new elements. The longer the interactions last, the more elements are formed. Age can then be estimated by measuring how many of the new cosmic ray-produced elements were present in pre-solar samples, Heck said. 13Based on examinations of this data, the researchers learned that some of the pre-solar particles were the oldest ever discovered. The team identified the age of 40 grains, most of which were estimated to be between 4.6 billion and 4.9 billion years old. 14These ages relate to the time when the first stars began to break up. Since that kind of star lived for up to 2.5 billion years, the stardust can be as old as up to seven billion years. 15The latest dating process confirms a scientific theory that predicted "a baby boom of stars" happened before the formation of our sun. 16"We have more young grains than we expected," Heck said. He added: "We basically came to the conclusion that there must have been a time in our galaxy when more stars formed than normal, and at the end of their lives they become dust producing." 17I'm Bryan Lynn. 18Bryan Lynn wrote this story for VOA Learning English, based on reports from Reuters, Agence France-Presse, Proceedings of the National Academy of Sciences and The Field Museum of Natural History. Ashley Thompson was the editor. 19We want to hear from you. Write to us in the Comments section, and visit our Facebook page. 20________________________________________________________________ 21Words in This Story 22meteorite - n. a piece of rock from outer space 23sample - n. a small amount of something that represents what it is like 24curator - n. a person who is in charge of a museum 25time capsule - n. a container filled with objects considered to be typical of a period in history and buried, so that it can be dug up and studied much later 26interact - v. to act upon one another 27baby boom - n. a large increase in the number of babies born in a particular place during a particular time 28grain - n. a very small piece of a hard substance 29conclusion - n. a decision made after a lot of consideration