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Voa02 lesson 31-60, (32) Oldest Material Discovered on Earth: 7 Billion Year Old Stardust

(32) Oldest Material Discovered on Earth: 7 Billion Year Old Stardust

Oldest Material Discovered on Earth: 7 Billion Year Old Stardust

Scientists 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.

Stardust 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.

The 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.

But until now, the age of the oldest stardust samples had not been confirmed.

Researchers at the museum reported their identification last week in Proceedings of the National Academy of Sciences.

“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.

The 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.

The 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.

The 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.

The researchers then examined samples for information that would help them identify what kinds of stars they came from and how old they were.

In space, dust interacts with cosmic rays -- high-energy particles that move through space at nearly the speed of light.

Philipp 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.

This artist's impression shows what the very distant young galaxy A2744_YD4 might look like. Observations using ALMA have shown that this galaxy, seen when the Universe was just 4 percent of its current age, is rich in dust. Such dust was produced by an e

Based 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.

These 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.

The latest dating process confirms a scientific theory that predicted “a baby boom of stars” happened before the formation of our sun.

“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."


(32) Oldest Material Discovered on Earth: 7 Billion Year Old Stardust

Oldest Material Discovered on Earth: 7 Billion Year Old Stardust

Scientists 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. 它是在 50 年前在澳大利亚从天上掉下来的陨石碎片中发现的。

Stardust is matter that forms as small particles in space when stars die. 星尘是恒星死亡时在太空中形成的小颗粒物质。 These particles can be used later to form new planetary bodies, including stars, planets and moons.

The meteorite pieces came down in September 1969 in the town of Murchison, in Australia's Victoria state. 陨石碎片于 1969 年 9 月在澳大利亚维多利亚州的默奇森镇落下。 Scientists with the Field Museum of Natural History in the American city of Chicago have long held the largest collection of these pieces. 美国芝加哥市菲尔德自然历史博物馆的科学家长期以来一直拥有这些作品的最大收藏。

But until now, the age of the oldest stardust samples had not been confirmed. 但直到现在,最古老的星尘样本的年龄还没有得到证实。

Researchers at the museum reported their identification last week in Proceedings of the National Academy of Sciences. 博物馆的研究人员上周在《美国国家科学院院刊》上报告了他们的身份。

“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. “这些是迄今为止发现的最古老的固体材料,它们告诉我们恒星是如何在我们的银河系中形成的,”他补充说。

The scientists said the microscopic particles were made of silicon carbide, the first mineral formed when a star cools. 科学家们说,这些微观粒子是由碳化硅制成的,这是恒星冷却时形成的第一种矿物。 All of the samples predate the formation of our own solar system, they noted. 他们指出,所有样本都早于我们自己的太阳系形成之前。

The 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.

The identification process first involved crushing the samples down into a fine dust. 识别过程首先涉及将样品粉碎成细粉尘。 The pieces were then mixed with acid, which left only the pre-solar particles. 然后将这些碎片与酸混合,仅留下前太阳粒子。

The researchers then examined samples for information that would help them identify what kinds of stars they came from and how old they were.

In space, dust interacts with cosmic rays -- high-energy particles that move through space at nearly the speed of light. 在太空中,尘埃与宇宙射线相互作用——高能粒子以接近光速的速度穿过太空。

Philipp Heck explained that some of these interactions result in the formation of new elements. Philipp Heck 解释说,其中一些相互作用导致了新元素的形成。 The longer the interactions last, the more elements are formed. 相互作用持续的时间越长,形成的元素就越多。 Age can then be estimated by measuring how many of the new cosmic ray-produced elements were present in pre-solar samples, Heck said. 赫克说,然后可以通过测量太阳前样本中存在多少新的宇宙射线产生的元素来估计年龄。

This artist's impression shows what the very distant young galaxy A2744_YD4 might look like. 这位艺术家的印象展示了非常遥远的年轻星系 A2744_YD4 的样子。 Observations using ALMA have shown that this galaxy, seen when the Universe was just 4 percent of its current age, is rich in dust. 使用 ALMA 进行的观测表明,当宇宙只有当前年龄的 4% 时,这个星系就含有丰富的尘埃。 Such dust was produced by an e

Based on examinations of this data, the researchers learned that some of the pre-solar particles were the oldest ever discovered. 根据对这些数据的检查,研究人员了解到,一些太阳前粒子是迄今为止发现的最古老的粒子。 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. 该团队确定了 40 颗谷物的年龄,其中大部分估计在 46 亿至 49 亿年之间。

These ages relate to the time when the first stars began to break up. 这些年龄与第一颗恒星开始分裂的时间有关。 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. 由于这种恒星的寿命长达 25 亿年,因此星尘的年龄可长达 70 亿年。

The latest dating process confirms a scientific theory that predicted “a baby boom of stars” happened before the formation of our sun. 最新的测年过程证实了一个科学理论,该理论预测“恒星婴儿潮”发生在我们的太阳形成之前。

“We have more young grains than we expected,” Heck said. “我们的新谷物比我们预期的要多,”赫克说。 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." 他补充说:“我们基本上得出的结论是,在我们的银河系中一定有一段时间形成的恒星比正常情况多,在它们生命的尽头,它们会产生尘埃。”