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Dust Older Than the Sun Sheds Light on Galactic History

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Hidden inside the famous Murchison meteorite are motes of stardust older than the Sun. A new analysis measured the ages of these stardust grains, which include the oldest solid material on Earth. The research also has revealed clues about the Milky Way’s past and how dust travels from star to star.

“The most exciting part is to be able to study the star formation history of our galaxy with presolar minerals extracted from Murchison,” said lead researcher Philipp Heck, Pritzker Associate Curator at the Field Museum of Natural History in Chicago. “Stardust is the oldest material to reach Earth, and from it, we can learn about our parent stars, the origin of the carbon in our bodies, the origin of the oxygen we breathe,” he added in a statement. “With stardust, we can trace that material back to the time before the Sun.”

The Dust of Stars, Literally

How does stardust form, and how does it find its way into a meteorite bound for Earth? The process begins, as the name suggests, inside a star.

Stars at the asymptotic giant branch stage have four distinct layers. The innermost layer (blue) is a core of inert carbon and oxygen. The second layer (green) is helium fusing into carbon and oxygen. The third layer (yellow) is hydrogen fusing into helium. The outermost and coolest layer (red) is inert hydrogen. Credit: National Optical Astronomy Observatory/Association of Universities for Research in Astronomy/National Science Foundation

Just before it dies, a star whose mass is less than 10 times that of the Sun will have layers like an onion. The layers—made of carbon, oxygen, helium, and hydrogen—are either fusing new elements or collapsing under their own weight. At this stage of a star’s life, known as the asymptotic giant branch (AGB), the very top layers of the star’s atmosphere are cool enough for dust to condense. That is stardust.

During the last 100,000 years of its life, the AGB star will puff out its atmosphere to create a beautiful planetary nebula. Some of the stardust, propelled by the nebula’s expansion, will flow farther outward.

Stardust made up a tiny percentage of the interstellar soup that birthed our solar system. Less than 200 parts per million survived to be incorporated into the Sun, planets, comets, and asteroids.

And, in 1969, a 100-kilogram chunk of one carbonaceous chondrite bore some of that stardust to Murchison in Victoria, Australia.

As Old As Dust

Researchers ground down a small part of the meteorite into a fine powder and separated the stardust from the solar system dust by their chemical compositions. They then measured the ages of the microscopic particles by determining how long the grains had been exposed to high-energy galactic cosmic rays.

Exposure to high-energy cosmic rays changes the surfaces of dust grains traveling through the galaxy. Grains are more heavily coated with the isotopes helium-3 and neon-21 the longer they exist outside the solar system. (The Sun’s magnetic field shields the grains once they arrive.)

This speck of stardust, seen here in a scanning electron micrograph, condensed in the atmosphere of a dying star. It is silicon carbide and measures only 8 micrometers on its longest side. Credit: Janaína N. Ávila

About 60% of the newly discovered grains predate the solar system by only 300 million years. Adding the age of the Sun, the presolar age of the grains, and the time it takes a star to reach the AGB stage, this dating suggests that the stars that made these grains were born about 7 billion years ago.

Moreover, the team estimates that the stars that made these grains must have been between 2 and 3 times the mass of the Sun. Smaller stars wouldn’t have reached the AGB stage before the solar system formed, and the radiation from larger stars would have prevented the grains from growing as big as they did, the team argues.

Some of the grains show signs that they traveled the galaxy in large clusters, which is consistent with observations of objects like the Egg Nebula, said coauthor Jennika Greer, a graduate student researcher at the Field Museum. In addition, 8% of the grains dated in the study are more than a billion years older than the Sun. One grain is more than 3 billion years older than the Sun, which, at more than 7 billion years, makes it the oldest solid material on Earth.

These results were published in Proceedings of the National Academy of Sciences of the United States of America on 13 January.

Piecing Together Galactic History

Astronomers are still trying to figure out how often the Milky Way forms stars and whether the rate is constant or whether it fluctuates. Previous studies, some based on theory and some on observations, have pointed to a period of slightly enhanced star formation about 7 billion years ago.

“Our age distribution also supports a heterogeneous star formation rate, something that is supported in high-resolution models,” said Greer. “With presolar grains, we can analyze objects, like stars and supernovae, and events, like star formation, not normally accessible by laboratory studies.”

“An amazing aspect of this finding is that it is based on direct measurement of decay products, while generally the evidence…is based on indirect chronological methods, which are ultimately linked to a stellar model or statistical assumptions,” Helio Rocha-Pinto told The Guardian. “Yet they are the main tools we have for dating stars since we cannot take them to the laboratory.” Rocha-Pinto, an astronomer at Observatório do Valongo at the Federal University of Rio de Janeiro in Brazil, was not involved with this research.

This project analyzed 40 presolar grains from the meteorite. “We have already started separating more large, datable presolar grains from Murchison,” Heck said. The researchers hope that future grains will have ages that let them look further back in time.

“With more ages,” Greer added, “I believe we will be able to resolve discrete events in our galaxy in addition to our evidence for one period of increased star production, much like that in zircon geochronology for solar system and terrestrial samples.”

—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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